Use the metric system and convert between metric units - Health Education Systems Admission Assessment HESI

1. A medication dose is 4 mcg/kg/min. It is administered to a patient weighing 75 kg. The medication is supplied in a bag containing 30 mg of the drug in 250 mL of solution. At what rate in mL/hr should the IV pump be set?
   Answer: 15 mL/hr This type of calculation tests your ability to convert between different drug concentration units and dosing rates - a critical skill for safe medication administration. You need to work systematically through unit conversions to find the pump rate. Start by calculating the total dose needed per minute: $4 \text{ mcg/kg/min} \times 75 \text{ kg} = 300 \text{ mcg/min}$ Next, determine the drug concentration in the IV bag. Convert 30 mg to mcg: $30 \text{ mg} = 30,000 \text{ mcg}$. So the concentration is $30,000 \text{ mcg} ÷ 250 \text{ mL} = 120 \text{ mcg/mL}$. Now find how much solution delivers the required dose: $300 \text{ mcg/min} ÷ 120 \text{ mcg/mL} = 2.5 \text{ mL/min}$ Finally, convert to mL/hr: $2.5 \text{ mL/min} \times 60 \text{ min/hr} = 15 \text{ mL/hr}$ Answer B (15 mL/hr) is correct. Answer A (1.5 mL/hr) represents forgetting to multiply by 60 when converting from minutes to hours. Answer C (22.5 mL/hr) likely comes from miscalculating the concentration or dose requirements. Answer D (25 mL/hr) suggests an error in the weight-based dose calculation or unit conversion. For HESI dosage calculations, always work methodically: calculate total dose needed, find drug concentration, determine volume needed per time unit, then convert to the requested units. Double-check your unit conversions - this is where most errors occur.
2. A vial contains 500,000 units of a drug in powder form. It is reconstituted with 2.3 mL of diluent to yield a final volume of 2.5 mL. The physician orders 125,000 units. How many milliliters should be administered?
   Answer: 0.63 mL Drug reconstitution problems test your ability to calculate dosages when medications are prepared from powder form. The key is finding the concentration after reconstitution, then using proportion to determine the volume needed. First, calculate the concentration of the reconstituted solution. You have 500,000 units dissolved in a final volume of 2.5 mL, so the concentration is $\frac{500,000 \text{ units}}{2.5 \text{ mL}} = 200,000 \text{ units/mL}$. Next, use proportion to find the volume needed for 125,000 units: $\frac{200,000 \text{ units}}{1 \text{ mL}} = \frac{125,000 \text{ units}}{x \text{ mL}}$ Cross multiply: $200,000x = 125,000$ $x = \frac{125,000}{200,000} = 0.625 \text{ mL}$ Rounded appropriately, this equals 0.63 mL, making B correct. Choice A (0.58 mL) likely results from calculation errors or rounding mistakes. Choice C (0.80 mL) might come from incorrectly using the diluent volume (2.3 mL) instead of final volume (2.5 mL) in your concentration calculation. Choice D (1.25 mL) probably results from confusing the setup—perhaps dividing 125,000 by 100,000 instead of 200,000. Remember that the final volume after reconstitution is what matters for concentration calculations, not just the diluent added. Always double-check your math by verifying: does 0.63 mL × 200,000 units/mL equal approximately 125,000 units? This backward calculation catches most errors.
3. A medication's concentration is 40 mg per 2 mL. A physician orders a dose of 0.3 grams. How many milliliters of the medication should be administered?
   Answer: 15 mL Medication dosage calculations require careful unit conversion and proportional reasoning. When you encounter these problems, always start by ensuring all units match before setting up your calculation. First, convert the ordered dose to the same units as the concentration. The order is for 0.3 grams, which equals 300 mg (since 1 gram = 1000 mg). Now you have a concentration of 40 mg per 2 mL and need to deliver 300 mg. Set up a proportion: $\frac{40 \text{ mg}}{2 \text{ mL}} = \frac{300 \text{ mg}}{x \text{ mL}}$ Cross multiply: $40x = 300 \times 2 = 600$ Solve for x: $x = \frac{600}{40} = 15 \text{ mL}$ This confirms answer B (15 mL) is correct. Looking at the wrong answers: A (7.5 mL) represents exactly half the correct amount, likely from miscalculating the proportion or forgetting to account for the full gram conversion. C (26.6 mL) appears to result from incorrectly treating the 0.3 grams as 0.3 mg instead of 300 mg, then overcompensating in the calculation. D (30 mL) seems to come from incorrectly assuming a 1:1 ratio between the decimal dose (0.3) and the concentration without proper unit conversion. Always write out your unit conversions explicitly and double-check that your final answer makes logical sense. In this case, since you need 7.5 times the base concentration (300 ÷ 40 = 7.5), you should need 7.5 times the base volume (7.5 × 2 = 15 mL).
4. A patient is to receive an IV infusion of 1.2 L of fluid over 8 hours. The IV set delivers 15 drops/mL. After 3 hours, how many milliliters of fluid should have been infused?
   Answer: 450 mL IV infusion calculations are common on the HESI exam and require you to work with rates and proportions to determine how much fluid should be administered over time. To solve this problem, start by identifying what you need to find: the volume that should be infused after 3 hours. Set up a proportion using the total volume and total time given. You have 1.2 L (which equals 1,200 mL) to be infused over 8 hours. Using the proportion: $\frac{1,200 \text{ mL}}{8 \text{ hours}} = \frac{x \text{ mL}}{3 \text{ hours}}$ Cross multiply: $8x = 1,200 \times 3 = 3,600$ Solving for x: $x = \frac{3,600}{8} = 450 \text{ mL}$ This confirms that 450 mL should have been infused after 3 hours, making D) 450 mL correct. Looking at the wrong answers: A) 150 mL represents only 1/8 of the total volume, suggesting confusion about the time fraction. B) 375 mL might result from miscalculating the hourly rate or making an arithmetic error in the proportion. C) 400 mL is close but likely comes from rounding errors or incorrect setup of the initial equation. Note that the drop factor (15 drops/mL) is irrelevant to this question—it's included as a distractor. For HESI IV calculation problems, always identify exactly what's being asked before getting caught up in extra information. Focus on setting up clear proportions with matching units.
5. A pharmacist needs to prepare a 0.25 L solution containing 5 g of a drug. How many milligrams of the drug would be in a 20 mL dose of this solution?
   Answer: 400 mg When you encounter dosage calculation problems, you're working with concentration and proportional reasoning. The key is to first determine the concentration of the solution, then calculate how much drug is in the specific dose volume. Start by finding the concentration of the prepared solution. You have 5 g of drug in 0.25 L of solution, so the concentration is $\frac{5 \text{ g}}{0.25 \text{ L}} = 20 \text{ g/L}$. Now convert this to a more useful unit for the 20 mL dose. Since 1 L = 1000 mL, the concentration becomes $\frac{20 \text{ g}}{1000 \text{ mL}} = 0.02 \text{ g/mL}$. For a 20 mL dose: $0.02 \text{ g/mL} \times 20 \text{ mL} = 0.4 \text{ g}$ Converting to milligrams: $0.4 \text{ g} \times 1000 \text{ mg/g} = 400 \text{ mg}$ Answer choice A (200 mg) represents half the correct amount, likely from miscalculating the concentration or dose volume. Answer choice B (250 mg) might result from incorrectly using the original 0.25 L volume in calculations without proper unit conversion. Answer choice D (500 mg) overshoots the correct value, possibly from confusion about decimal placement or unit conversions. For HESI dosage calculations, always work systematically: establish concentration first, ensure consistent units throughout, then apply the concentration to your target volume. Double-check unit conversions between grams and milligrams, and liters and milliliters, as these are common error points.
6. A child is prescribed a liquid antibiotic with a dosage of 15 mg/kg per day, divided into two equal doses. The child weighs 20 kg. The antibiotic suspension has a concentration of 0.1 g per 5 mL. How many milliliters should be administered for each dose?
   Answer: 7.5 mL When you encounter pediatric dosage calculations, you need to work systematically through weight-based dosing, daily totals, and individual dose volumes. This question tests your ability to convert between units while calculating the correct volume for administration. Start by calculating the total daily dose: $15 \text{ mg/kg/day} \times 20 \text{ kg} = 300 \text{ mg/day}$. Since this is divided into two equal doses, each dose contains $300 \text{ mg} ÷ 2 = 150 \text{ mg}$. Next, convert the concentration to consistent units. The suspension contains 0.1 g per 5 mL, which equals 100 mg per 5 mL (since 0.1 g = 100 mg). To find the volume needed for 150 mg, set up a proportion: $\frac{100 \text{ mg}}{5 \text{ mL}} = \frac{150 \text{ mg}}{x \text{ mL}}$. Cross-multiplying: $100x = 750$, so $x = 7.5 \text{ mL}$. Choice A (3.75 mL) represents half the correct volume—you might get this if you forgot to divide the daily dose by 2 and then made an error in your final calculation. Choice C (15 mL) occurs if you incorrectly calculated the concentration as 50 mg per 5 mL instead of 100 mg per 5 mL. Choice D (30 mL) results from using the total daily dose (300 mg) without dividing by 2, then applying the wrong concentration. The correct answer is B (7.5 mL). For HESI dosage calculations, always write out each step clearly: calculate total daily dose, divide by frequency, convert units to match, then solve for volume. Double-check your unit conversions—they're the most common source of errors.
7. A patient's intake and output chart shows: intake of 1.25 L oral fluids and 0.485 L IV fluids; output of 890 mL urine and 0.34 L from drainage tube. If the fluid balance must be calculated in mL and a positive balance above 500 mL requires intervention, what action is needed?
   Answer: Intervention required, balance shows 505 mL positive fluid retention Fluid balance calculations are essential nursing skills that require careful unit conversion and mathematical precision. When you encounter intake and output questions, always convert everything to the same units first before calculating the balance. Let's work through this step-by-step. First, convert all values to mL: intake includes 1.25 L oral fluids (1,250 mL) plus 0.485 L IV fluids (485 mL) for a total intake of 1,735 mL. Output includes 890 mL urine plus 0.34 L drainage (340 mL) for a total output of 1,230 mL. The fluid balance equals intake minus output: 1,735 mL - 1,230 mL = 505 mL positive balance. Since this patient has a positive balance of 505 mL, which exceeds the 500 mL threshold, intervention is required. Answer D correctly identifies both the need for intervention and the accurate calculation of 505 mL. Answer A uses an incorrect calculation of 485 mL, likely confusing one of the individual fluid values with the final balance. Answer B shows 405 mL, suggesting a computational error in either the intake or output totals. Answer C calculates 565 mL, which appears to involve an addition error when combining the fluid values. For HESI fluid balance questions, always double-check your unit conversions (remember 1 L = 1,000 mL) and verify your arithmetic carefully. These questions test both your mathematical accuracy and clinical judgment about when patient interventions become necessary.
8. A patient is prescribed 0.125 mg of a medication. The pharmacy dispenses tablets that each contain 250 micrograms (mcg). How many tablets should the nurse administer?
   Answer: 0.5 tablets When you encounter medication dosage calculations, you need to convert units to match and then use dimensional analysis to find how many tablets to give. First, convert the prescribed dose to the same units as the tablets. The prescription is 0.125 mg, and the tablets contain 250 mcg each. Since 1 mg = 1,000 mcg, you convert: $0.125 \text{ mg} \times 1,000 \text{ mcg/mg} = 125 \text{ mcg}$ Now use the formula: $\text{Tablets needed} = \frac{\text{Dose prescribed}}{\text{Dose per tablet}} = \frac{125 \text{ mcg}}{250 \text{ mcg/tablet}} = 0.5 \text{ tablets}$ Looking at the wrong answers: Choice A (0.25 tablets) results from incorrectly dividing 125 by 500 instead of 250, possibly confusing the tablet strength. Choice C (1 tablet) happens when you forget to convert units and mistakenly think 0.125 mg equals 250 mcg. Choice D (2 tablets) occurs when you flip the fraction and divide 250 by 125, a common error when rushing through calculations. The correct answer is B (0.5 tablets). For HESI dosage calculations, always follow this three-step approach: convert to matching units first, set up your dimensional analysis carefully, and double-check by asking if your answer makes sense. Since the prescribed dose (125 mcg) is exactly half the tablet strength (250 mcg), half a tablet should immediately seem reasonable.
9. A nurse needs to administer 2.5 g of medication, but the available tablets are 500 mg each. After calculating the required number of tablets, the nurse discovers that only 250 mg tablets are available instead. How many additional tablets beyond the original calculation will be needed?
   Answer: 5 additional tablets First, convert 2.5 g to mg: 2.5 g × 1000 mg/g = 2500 mg. With 500 mg tablets: 2500 ÷ 500 = 5 tablets needed. With 250 mg tablets: 2500 ÷ 250 = 10 tablets needed. Additional tablets needed: 10 - 5 = 5 tablets. Choice B represents the total tablets needed with 250 mg, not additional. Choice C incorrectly adds the two calculations. Choice D doubles the total needed.
10. A storage tank holds 1.5 kiloliters (kL) of a disinfectant. If 300 L are used on day one and 45,000 mL are used on day two, how many liters remain in the tank?
    Answer: 1155 L When you encounter unit conversion problems on the HESI, you need to convert everything to the same units before performing calculations. This question tests your ability to work with metric volume units and track changes to an initial quantity. Start by converting all measurements to liters. The tank initially holds 1.5 kiloliters. Since 1 kL = 1,000 L, you have $1.5 \times 1,000 = 1,500$ L initially. Day one usage is already given as 300 L. For day two, convert 45,000 mL to liters: since 1 L = 1,000 mL, you get $45,000 ÷ 1,000 = 45$ L. Now calculate what remains: $1,500 - 300 - 45 = 1,155$ L. Looking at the wrong answers: Choice B (1200 L) likely results from incorrectly converting the initial amount or making an arithmetic error in subtraction. Choice C (1425 L) suggests you only subtracted one day's usage, probably forgetting to account for both days. Choice D (1455 L) indicates a conversion error with the milliliters—perhaps dividing by 100 instead of 1,000, giving 450 L instead of 45 L for day two usage. Choice A (1155 L) correctly accounts for all conversions and subtractions. For HESI math problems involving multiple units, always convert everything to the same unit first—usually the one requested in the answer. Double-check your metric conversions (kilo = 1,000, milli = 1/1,000) and verify you've accounted for all given information before selecting your answer.
11. A patient is prescribed 2 mg of a medication per kilogram of body weight. The patient weighs 82 kg. The medication is supplied in vials containing 0.2 g of the medication. How many vials are needed for the dose?
    Answer: 0.82 vials This question tests your ability to perform multi-step dosage calculations with unit conversions, a critical skill for safe medication administration. To solve this, you need to calculate the total dose required, then determine how many vials provide that amount. Start by finding the patient's total dose: $2 \text{ mg/kg} \times 82 \text{ kg} = 164 \text{ mg}$ Next, convert the vial contents to the same units. Each vial contains 0.2 g, which equals $0.2 \text{ g} \times 1000 \text{ mg/g} = 200 \text{ mg}$ Finally, divide the required dose by the amount per vial: $\frac{164 \text{ mg}}{200 \text{ mg/vial}} = 0.82 \text{ vials}$ Answer A (0.82 vials) is correct—this is the exact calculation result. Answer B (0.91 vials) likely comes from incorrectly using 180 mg per vial instead of 200 mg, possibly from a unit conversion error. Answer C (1.22 vials) suggests someone divided 200 by 164 instead of 164 by 200, essentially flipping the calculation. Answer D (1.64 vials) results from forgetting to convert grams to milligrams and dividing 164 mg by 0.1 g (treating 0.1 as the numerical value without proper units). Study tip: Always work systematically through dosage calculations: calculate total dose needed, convert all units to match, then divide. Double-check your unit conversions—mixing grams and milligrams is a common source of errors on the HESI exam.
12. A patient is instructed to take 750 mg of a medication twice a day for one week. The medication is dispensed in grams. How many total grams will the patient consume in one week?
    Answer: 10.5 g This question tests your ability to convert between units (milligrams to grams) and perform dosage calculations over time—two essential skills in healthcare that frequently appear on the HESI exam. Let's work through this step-by-step. First, calculate the total milligrams consumed daily: 750 mg taken twice daily equals $750 \times 2 = 1,500$ mg per day. Over one week (7 days), the total is $1,500 \times 7 = 10,500$ mg. Since the medication is dispensed in grams, you must convert milligrams to grams. Remember that 1 gram = 1,000 milligrams, so: $10,500 \text{ mg} \div 1,000 = 10.5$ grams. This confirms answer choice B is correct. Now let's examine why the other options are wrong. Choice A (5.25 g) represents only half the correct answer—you might get this if you calculated the weekly dose but forgot to account for taking the medication twice daily. Choice C (52.5 g) is five times too large; this error typically occurs when students multiply instead of divide during unit conversion, treating 1 mg as equal to 1,000 g instead of the reverse. Choice D (105 g) is ten times too large, suggesting a decimal place error or confusion about the conversion factor. For HESI dosage calculations, always organize your work in clear steps: identify the dose per administration, calculate daily total, multiply by duration, then convert units carefully. Double-check your unit conversions—medication errors often stem from misplaced decimals or incorrect conversion factors.
13. A laboratory solution has a concentration of 1.5 grams per liter (g/L). What is this concentration in micrograms per milliliter (mcg/mL)?
    Answer: 1500 mcg/mL Unit conversion questions are fundamental in healthcare calculations, where you'll frequently need to convert between different units of concentration for medications and laboratory values. The key is setting up conversion factors systematically. To convert 1.5 g/L to mcg/mL, you need two conversions: grams to micrograms and liters to milliliters. Start with the mass conversion: 1 gram = 1,000,000 micrograms ($10^6$ mcg). Then the volume conversion: 1 liter = 1,000 milliliters. Set up your conversion: $1.5 \frac{\text{g}}{\text{L}} \times \frac{1,000,000 \text{ mcg}}{1 \text{ g}} \times \frac{1 \text{ L}}{1,000 \text{ mL}}$ This gives you: $\frac{1.5 \times 1,000,000}{1,000} = \frac{1,500,000}{1,000} = 1,500 \text{ mcg/mL}$ Answer choice A (1.5 mcg/mL) represents no conversion at all—simply changing the units without adjusting the numerical value. Answer choice B (15 mcg/mL) suggests you converted grams to micrograms incorrectly, perhaps using $10^4$ instead of $10^6$. Answer choice C (150 mcg/mL) indicates you might have converted grams to milligrams ($10^3$) instead of micrograms, or made an error in the volume conversion. The correct answer is D (1500 mcg/mL). Study tip: For HESI unit conversions, always write out your conversion factors completely and check that units cancel properly. Remember the metric prefixes: milli = $10^{-3}$, micro = $10^{-6}$. Practice converting between common medical units until the conversions become automatic.
14. A roll of medical tape is 2.5 meters long. A nurse uses three strips of tape measuring 15 cm, 280 mm, and 0.4 m. What length of tape, in centimeters, remains on the roll?
    Answer: 167 cm Unit conversion problems like this are common on the HESI and test your ability to work with different metric measurements systematically. The key is converting everything to the same unit before doing any arithmetic. Start by converting all measurements to centimeters since that's what the question asks for. The roll begins at 2.5 meters = 250 cm. Now convert each strip used: 15 cm stays as 15 cm, 280 mm becomes 28 cm (since 1 cm = 10 mm), and 0.4 m becomes 40 cm (since 1 m = 100 cm). Calculate the total tape used: $15 + 28 + 40 = 83 \text{ cm}$ Subtract from the original length: $250 - 83 = 167 \text{ cm}$ remaining. Looking at the wrong answers: Choice A (83 cm) represents the total amount of tape used, not what remains—this catches students who stop calculating halfway through. Choice C (184 cm) likely results from incorrectly converting 280 mm as 2.8 cm instead of 28 cm, leading to $250 - (15 + 2.8 + 40) = 192.2$, which students might round to a nearby option. Choice D (207 cm) could come from converting 0.4 m as 4 cm instead of 40 cm, giving $250 - (15 + 28 + 4) = 203$, again leading to selecting the closest option. For HESI math problems, always write out your unit conversions explicitly and double-check each step. Most errors come from rushing through conversions or confusing which operation to perform with your final calculated values.
15. A clinic's monthly supply of a vaccine is 0.8 L. If the average dose is 500 microliters (µL), how many full doses can be administered from the monthly supply?
    Answer: 1600 When you encounter dosage calculation problems on the HESI exam, you're working with unit conversions and basic division. The key is ensuring all units match before performing calculations. You have 0.8 L of vaccine and need to determine how many 500 µL doses you can extract. First, convert everything to the same unit. Since the dose is in microliters, convert the supply: 0.8 L = 800 mL = 800,000 µL (remember: 1 L = 1,000 mL, and 1 mL = 1,000 µL). Now divide the total supply by the dose size: $\frac{800,000 \text{ µL}}{500 \text{ µL/dose}} = 1,600 \text{ doses}$ Answer B (1600) is correct. Answer A (160) represents a calculation error where you likely divided 800 mL by 500 µL without proper unit conversion, or forgot one conversion step. Answer C (16000) occurs if you incorrectly converted liters to microliters, perhaps using 1 L = 10,000 µL instead of 1,000,000 µL. Answer D (160000) suggests you multiplied instead of divided, or made multiple unit conversion errors. For HESI dosage calculations, always write out your unit conversions step-by-step and double-check that units cancel properly in your final calculation. Practice converting between liters, milliliters, and microliters until it becomes automatic—these conversions appear frequently on nursing exams, and small errors in unit conversion can lead you to choose dramatically wrong answers.
16. A syringe contains 15 mL of a solution with 2.4 mg/mL concentration. The nurse draws out 0.008 L and administers it to the patient. How many micrograms of medication were administered?
    Answer: 19,200 μg of medication administered Dosage calculation problems test your ability to convert between units and apply concentration formulas systematically. When you encounter medication calculations with different units, always convert to consistent units first, then apply the concentration relationship. Start by converting the volume drawn: 0.008 L = 8 mL (since 1 L = 1000 mL). Now you can work with consistent units throughout the problem. Use the concentration formula: $\text{Amount} = \text{Concentration} \times \text{Volume}$ The amount administered = 2.4 mg/mL × 8 mL = 19.2 mg Finally, convert to micrograms: 19.2 mg × 1000 μg/mg = 19,200 μg Looking at the wrong answers: Choice A (21,600 μg) likely results from incorrectly using 9 mL instead of 8 mL in the calculation. Choice C (24,000 μg) represents using 10 mL volume, possibly from misconverting 0.008 L or rounding errors. Choice D (28,800 μg) suggests using 12 mL volume, which could come from confusing the total syringe volume (15 mL) with the amount drawn, or making multiple conversion errors. The correct answer is B: 19,200 μg. For HESI dosage calculations, always work methodically: convert all units to be consistent first, apply the concentration formula second, then convert to the requested units last. Write out each step to avoid the unit conversion errors that create most wrong answer choices in these problems.
17. Which of the following measurements represents the greatest mass?
    Answer: 450,000 mg When you encounter unit conversion problems, the key is converting everything to the same unit before comparing. Mass problems often mix units like kilograms, grams, milligrams, and micrograms, so you need to establish a common baseline. Let's convert everything to grams for easy comparison: Choice A: 450,000 mg = 450,000 ÷ 1,000 = 450 g (since 1,000 mg = 1 g) Choice B: 4,500,000 mcg = 4,500,000 ÷ 1,000,000 = 4.5 g (since 1,000,000 mcg = 1 g) Choice C: 0.045 kg = 0.045 × 1,000 = 45 g (since 1 kg = 1,000 g) Choice D: 45.5 g = 45.5 g (already in grams) Now comparing: 450 g > 45.5 g > 45 g > 4.5 g Choice A (450,000 mg = 450 g) represents the greatest mass. Choice B looks deceptively large because of the high number (4,500,000), but micrograms are extremely small units. Choice C might fool you if you forget that 0.045 kg is less than 1 kilogram, making it only 45 grams. Choice D is straightforward but much smaller than choice A. For HESI math problems involving units, always convert to a familiar base unit first—usually grams for mass, meters for length, or liters for volume. Watch out for answer choices with very large numbers in small units (like micrograms) or small decimal numbers in large units (like kilograms), as these are common distractors designed to test your conversion skills.
18. A patient is on a fluid restriction of 1.2 L per 24 hours. The patient has consumed 350 mL, 0.2 L, and 15 cL. How many more liters of fluid can the patient consume?
    Answer: 0.5 L When you encounter fluid restriction problems, you need to master unit conversions and basic arithmetic to track patient safety accurately. Fluid restrictions are critical in healthcare for patients with heart failure, kidney disease, or other conditions where excess fluid can be dangerous. First, convert all consumed fluids to the same unit as the restriction (liters). The patient consumed: - 350 mL = 0.35 L (divide by 1000) - 0.2 L = 0.2 L (already in liters) - 15 cL = 0.15 L (centiliters ÷ 100 = liters) Total consumed: $0.35 + 0.2 + 0.15 = 0.7 \text{ L}$ Remaining allowance: $1.2 - 0.7 = 0.5 \text{ L}$ Choice A (0.5 L) is correct. Choice B (0.7 L) represents the total amount already consumed, not the remaining allowance. This is a common trap where students confuse what's been used with what's left. Choice C (0.75 L) likely results from incorrectly converting 15 cL as 0.25 L instead of 0.15 L, then subtracting 0.45 L from 1.2 L. Choice D (1.13 L) appears to come from subtracting only some consumed fluids or making multiple conversion errors, resulting in an impossible answer since it exceeds the daily restriction. Study tip: Always convert to a common unit first, double-check your conversions (mL ÷ 1000 = L; cL ÷ 100 = L), and verify your final answer makes logical sense within the restriction limit.
19. A nurse records a patient's fluid intake from three sources: a 0.5 L bottle of water, a 240 mL cup of coffee, and a 125 mL bowl of soup. If 150 mL of water remains in the bottle, what was the patient's total fluid intake in milliliters?
    Answer: 715 mL Fluid intake calculations are fundamental nursing skills that require careful attention to what the patient actually consumed versus what was provided. When calculating total fluid intake, you must determine how much fluid entered the patient's body, not how much was initially available. Let's work through this systematically. The patient had three fluid sources: Water bottle: Started with 0.5 L (500 mL), with 150 mL remaining. Therefore, the patient consumed: $500 - 150 = 350 \text{ mL}$ Coffee: The patient drank the entire 240 mL cup. Soup: The patient consumed the entire 125 mL bowl. Total fluid intake: $350 + 240 + 125 = 715 \text{ mL}$ Looking at the incorrect options: A) 365 mL likely represents adding only the coffee and soup (240 + 125) while forgetting the water entirely. B) 515 mL appears to be the result of adding all three original amounts but subtracting the remaining water incorrectly (500 + 240 + 125 - 150 = 715, but perhaps miscalculated). D) 865 mL represents the common error of adding the full 500 mL from the bottle instead of subtracting what remained (500 + 240 + 125 = 865). Study tip: Always distinguish between "provided" and "consumed" in fluid calculations. When containers have leftovers, subtract the remainder from the original amount. Double-check your unit conversions (L to mL) and ensure you're accounting for actual intake, not just what was offered to the patient.
20. A wound is measured to be 6.4 cm long and 35 mm wide. What is the area of the wound in square millimeters (mm²)?
    Answer: 2240 mm² When you encounter wound measurement problems in healthcare, you're working with basic area calculations while managing unit conversions. The key is ensuring all measurements are in the same units before calculating. To find the area of this rectangular wound, you need to multiply length × width. However, the measurements are given in different units: 6.4 cm long and 35 mm wide. Since the answer choices are in square millimeters, convert everything to millimeters first. Converting the length: 6.4 cm × 10 mm/cm = 64 mm Now calculate the area: $64 \text{ mm} × 35 \text{ mm} = 2240 \text{ mm}^2$ Looking at the wrong answers reveals common calculation errors. Choice A (224 mm²) represents multiplying 6.4 × 35 without converting units—a unit conversion oversight that's off by a factor of 10. Choice B (990 mm²) might result from adding the dimensions instead of multiplying them, then applying some conversion factor incorrectly. Choice D (6435 mm²) appears to come from concatenating the numbers (6.4 and 35) rather than performing the proper mathematical operation. The correct answer is C (2240 mm²). For HESI success, always check that your units match before calculating, and remember that area calculations require multiplication, not addition. When dealing with wound care documentation, precision in measurements and calculations is crucial for tracking healing progress, so practice converting between centimeters and millimeters until it becomes automatic.

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