Solve percent increase/decrease problems - Health Education Systems Admission Assessment HESI

A nurse measures a wound as 4.5 cm long. The actual length, confirmed by a supervisor, is 4.0 cm. What is the nurse's percent error relative to the actual length?
Answer: 12.5% Percent error questions test your ability to calculate measurement accuracy, a crucial skill in healthcare where precise documentation affects patient care and treatment decisions. To find percent error, use this formula: $\text{Percent Error} = \frac{|\text{Measured Value} - \text{Actual Value}|}{|\text{Actual Value}|} \times 100\%$ Here, the measured value is 4.5 cm and the actual value is 4.0 cm. Substituting: $\text{Percent Error} = \frac{|4.5 - 4.0|}{|4.0|} \times 100\% = \frac{0.5}{4.0} \times 100\% = 0.125 \times 100\% = 12.5\%$ Answer A (0.5%) represents the absolute difference between measurements but ignores the percentage calculation entirely. Answer B (11.1%) comes from incorrectly using the measured value as the denominator: $\frac{0.5}{4.5} \times 100\% = 11.1\%$ . This is a common error—always use the actual (true) value in the denominator. Answer D (88.9%) likely results from calculating $\frac{4.0}{4.5} \times 100\%$ , which gives the measured accuracy percentage rather than the error percentage. The correct answer is C (12.5%). Remember that percent error always uses the actual or accepted value as the reference point in the denominator. In healthcare settings, you'll encounter similar calculations when evaluating instrument calibration, medication dosing accuracy, and quality control measures. Practice identifying which value represents the "true" or reference measurement.
A hospital's medication inventory shows that the stock of acetaminophen decreased from 2,400 tablets to 1,800 tablets over one month, while ibuprofen stock increased from 1,600 tablets to 2,080 tablets during the same period. What is the difference between the percent change in ibuprofen stock and the percent change in acetaminophen stock?
Answer: 55% First, calculate the percent change for acetaminophen: (1,800 - 2,400) ÷ 2,400 × 100 = -25% (decrease). Next, calculate the percent change for ibuprofen: (2,080 - 1,600) ÷ 1,600 × 100 = +30% (increase). The difference between the percent changes is 30% - (-25%) = 55%. Choice B (50%) results from incorrectly adding the absolute values. Choice C (45%) comes from calculation errors in the individual percentages. Choice D (40%) represents the sum of absolute values with computational mistakes.
An IV drip rate is increased by 20% to a new rate of 120 mL/hr. What was the original drip rate?
Answer: 100 mL/hr When you encounter percentage increase problems in healthcare calculations, you're working backwards from the final result to find the original value. This type of problem tests your ability to set up and solve equations involving percentages. Let's call the original drip rate $x$ . If the rate increased by 20%, the new rate equals the original rate plus 20% of the original rate. This gives us the equation: $x + 0.20x = 120$ . Combining like terms: $1.20x = 120$ . Solving for $x$ : $x = 120 ÷ 1.20 = 100$ mL/hr. You can verify this: if the original rate was 100 mL/hr, a 20% increase would be $100 × 0.20 = 20$ mL/hr, making the new rate $100 + 20 = 120$ mL/hr. ✓ Now let's examine why the other options are incorrect. Choice A (96 mL/hr) represents a common error where students subtract 20% from 120 instead of working backwards ( $120 × 0.80 = 96$ ). Choice C (108 mL/hr) might result from incorrectly calculating $120 - 12$ after finding 10% of 120. Choice D (144 mL/hr) comes from mistakenly adding 20% to 120 instead of recognizing that 120 is already the increased amount. Remember this key strategy: when a value has already been increased by a percentage, divide by $(1 + \text{percentage as decimal})$ to find the original. For decreases, divide by $(1 - \text{percentage as decimal})$ . This backward-calculation skill is essential for medication dosing problems on the HESI.
The concentration of a disinfectant solution is increased from 0.5% to 0.75%. What is the percent increase in the concentration?
Answer: 50% When you encounter percent increase problems, you're calculating how much a value has grown relative to its original amount. The key formula is: percent increase = $\frac{\text{new value} - \text{original value}}{\text{original value}} \times 100\%$ To solve this problem, identify your values: the original concentration is 0.5% and the new concentration is 0.75%. The actual increase is 0.75% - 0.5% = 0.25%. Now apply the formula: $\frac{0.25}{0.5} \times 100\% = 0.5 \times 100\% = 50\%$ Looking at the wrong answers: Choice A (25%) represents a common error where students calculate the absolute increase (0.25%) and mistakenly treat it as the percent increase without dividing by the original value. Choice B (33.3%) occurs when students incorrectly use the new value as the denominator instead of the original value: $\frac{0.25}{0.75} = 33.3\%$ . Choice D (75%) is the final concentration value itself, which some students might select if they confuse the question's intent. The correct answer is C (50%) because the concentration increased by 0.25 percentage points, which represents a 50% increase from the original 0.5% concentration. Remember this pattern: percent increase problems always require you to divide the change by the original value, not the new value. Watch for this distinction on math problems involving growth rates, dosage changes, or concentration modifications—it's a frequent source of errors on healthcare exams.
The cost of a certain medical procedure was reduced from $2,500 to $2,125. What was the percentage reduction in cost?
Answer: 15.0% When calculating percentage reduction, you need to find how much the value decreased relative to the original amount. This is a fundamental skill for healthcare professionals who must interpret cost analyses, dosage reductions, and statistical data. To find the percentage reduction, use this formula: $\text{Percentage reduction} = \frac{\text{Original value} - \text{New value}}{\text{Original value}} \times 100\%$ Here, the original cost was $2,500 and the new cost is $2,125. The reduction in dollars is: $2,500 - $2,125 = $375 Now calculate: $\frac{375}{2,500} \times 100\% = 0.15 \times 100\% = 15.0\%$ This confirms that A) 15.0% is correct. Let's examine why the other options are wrong. B) 17.6% might result from incorrectly using the new value ($2,125) as the denominator instead of the original value. This is a common error that inflates the percentage. C) 37.5% is far too large and might come from calculation errors or confusion about the formula. D) 85.0% represents the remaining percentage of the original cost ($2,125 ÷ $2,500 = 85%), not the reduction. Study tip: Always remember that percentage reduction uses the original value as the denominator, not the new value. A quick reasonableness check helps too—since $375 is much less than half of $2,500, the percentage should be well under 50%, immediately eliminating options C and D.
A nurse's hourly wage increased from $28.50 to $32.20. If she works 36 hours per week, what is her percent increase in weekly earnings, and how much additional money does she earn per week?
Answer: 12.98% increase, $133.20 additional weekly Percentage increase problems on the HESI often test your ability to calculate both the percent change and the absolute dollar difference. When you see wage increase questions, you need to find the new weekly earnings, compare them to the old weekly earnings, then calculate the percentage change. First, calculate the weekly earnings before and after the raise. Original weekly earnings: $28.50 × 36 = \$1,026$ . New weekly earnings: $32.20 × 36 = \$1,159.20$ . The additional weekly earnings are: $1,159.20 - 1,026 = \$133.20$ . To find the percent increase, use the formula: $\frac{\text{new value - old value}}{\text{old value}} × 100\%$ . This gives us: $\frac{133.20}{1,026} × 100\% = 12.98\%$ . Option A calculates 13.68% increase with $140 additional weekly earnings - this appears to use incorrect hourly calculations or rounding errors. Option B shows 13% with $135 additional - this likely rounds the percentage too early in the calculation, leading to compounding errors in the dollar amount. Option D gives 15% with $153.60 additional - this significantly overestimates both values, possibly from calculation errors in the basic multiplication steps. Option C correctly shows 12.98% increase and $133.20 additional weekly earnings, matching our precise calculations. For HESI math problems involving wages and percentages, always calculate the exact dollar amounts first, then use those precise figures for your percentage calculations. Avoid premature rounding, as it can lead you to attractive but incorrect answer choices.
A patient's resting heart rate increased from 60 beats per minute (bpm) to 75 bpm. Later, it decreased from 75 bpm back to 60 bpm. Which statement accurately compares the percent increase and percent decrease?
Answer: The percent increase was greater than the percent decrease. When you encounter percent change problems, remember that the baseline (starting value) matters crucially because it becomes your denominator. Even when the absolute change is identical, different baselines create different percentages. Let's calculate both changes step by step. For the increase from 60 to 75 bpm: the change is 15 bpm, so the percent increase is $\frac{15}{60} \times 100\% = 25\%$ . For the decrease from 75 to 60 bpm: the change is again 15 bpm, but now the percent decrease is $\frac{15}{75} \times 100\% = 20\%$ . The percent increase (25%) was indeed greater than the percent decrease (20%). Option A is incorrect because while the absolute changes were equal (15 bpm each direction), the different baselines (60 vs. 75) create different percentages. Option B reverses the relationship—the increase was actually larger, not smaller, than the decrease. Option D is wrong because we have all the information needed: the starting values and ending values for both changes. This asymmetry in percent changes is why stock market recoveries often take longer than crashes. If a stock drops 50%, it needs to gain more than 50% to return to its original value because the baseline has changed. On the HESI, percent change questions frequently test whether you recognize that equal absolute changes don't create equal percent changes when the baselines differ. Always identify your baseline carefully and remember that percentage calculations depend entirely on what denominator you're using.
A hospital's supply budget was cut by 10% last year. This year, the new budget was increased by 10%. What is the net percentage change in the budget over the two-year period?
Answer: A 1% decrease When you encounter percentage change problems involving multiple years, resist the temptation to simply add or subtract the percentages. Sequential percentage changes compound, meaning each change applies to the already-modified amount, not the original value. Let's work through this step-by-step. Say the original budget was $100,000. After a 10% cut, the budget becomes: $100,000 - (10% × $100,000) = $100,000 - $10,000 = $90,000. The following year, the budget increases by 10%, but this 10% applies to the reduced amount of $90,000, not the original $100,000: $90,000 + (10% × $90,000) = $90,000 + $9,000 = $99,000. Comparing the final amount ($99,000) to the original ($100,000): $\frac{99,000 - 100,000}{100,000} × 100\% = -1\%$ Therefore, choice A (a 1% decrease) is correct. Choice B (no change) represents the common misconception that +10% and -10% cancel out perfectly. Choice C (1% increase) mistakes the direction of the net change. Choice D (20% increase) incorrectly adds the absolute values of both percentages without considering the compounding effect. Study tip: For sequential percentage problems on the HESI, always calculate each step using the actual modified amount, not the original value. The phrase "of the new amount" should trigger this approach. Practice with concrete numbers to avoid the trap of thinking percentage changes are simply additive.
A report states that a patient's cholesterol level decreased by 20% to a new level of 160 mg/dL. Which calculation correctly determines the patient's original cholesterol level?
Answer: $160 \div (1 - 0.20)$ When you encounter percentage decrease problems in healthcare calculations, you need to work backwards from the final value to find the original amount. Think of this systematically: if something decreased by 20%, then the new value represents 80% of the original. Let's set up the relationship. If the original cholesterol level was $x$ , then after a 20% decrease: $x \times 0.80 = 160$ . To find $x$ , you divide both sides by 0.80: $x = 160 \div 0.80$ . Since $0.80 = (1 - 0.20)$ , this becomes $160 \div (1 - 0.20)$ , which matches answer choice D. Let's verify: $160 \div 0.80 = 200$ . Check: $200 \times 0.20 = 40$ (the decrease), and $200 - 40 = 160$ ✓ Now for the wrong answers: Choice A ( $160 \times 1.20$ ) gives you 192, which would be a 20% increase from 160, not finding the original level. Choice B ( $160 \times 0.80$ ) gives you 128, which represents taking another 20% decrease from the already-decreased value. Choice C ( $160 \div 1.20$ ) gives you 133.33, which incorrectly treats the decrease as if you're dividing by 120% instead of the remaining 80%. For HESI percentage problems, remember this pattern: when something decreases by a percentage, the final value equals the original times (1 minus the percentage). To find the original, divide the final value by (1 minus the percentage). This applies to medication dosing, lab values, and vital signs calculations.
A pharmaceutical company's stock was valued at $50 per share. It increased by 20% in the first quarter and then decreased by 15% in the second quarter. What was the final value of the stock per share after the second quarter?
Answer: $51.00 When you encounter percentage change problems, remember that each percentage change applies to the value at that point in time, not the original value. You must calculate changes sequentially. Start with the initial stock value of $50 per share. In the first quarter, it increased by 20%: $50 × 1.20 = 60$ The stock is now worth $60 per share. In the second quarter, it decreased by 15% from this new value of $60: $60 × 0.85 = 51$ The final value is $51.00 per share. Choice A ($49.50) represents a common error where students incorrectly subtract 15% from the original $50 value instead of from the $60 value after the first quarter increase. Choice C ($52.50) likely comes from incorrectly calculating the second quarter as a 10% decrease instead of 15%, or from arithmetic errors in the percentage calculations. Choice D ($55.00) suggests the student only calculated the first quarter increase and forgot to apply the second quarter decrease entirely. The key trap here is forgetting that percentage changes are cumulative - each change builds on the previous result, not the original amount. Always work step-by-step through sequential percentage changes, using your calculated result from each step as the base for the next calculation. This type of compound percentage problem appears frequently on standardized tests, so practice identifying when changes should be applied sequentially versus simultaneously.
A patient is advised to reduce their daily calorie intake of 2,200 calories by 20%. After one month, they are further advised to reduce the new daily intake by another 10%. What is the final target daily calorie intake?
Answer: 1584 Multi-step percentage problems are common on the HESI exam and test your ability to apply percentage reductions sequentially. The key insight is that each percentage reduction applies to the current amount, not the original amount. Let's work through this step-by-step. Starting with 2,200 calories, the first reduction is 20%. Calculate this as: $2,200 × 0.20 = 440$ calories to remove. This gives us $2,200 - 440 = 1,760$ calories after the first month. The second reduction of 10% applies to this new amount of 1,760 calories, not the original 2,200. Calculate: $1,760 × 0.10 = 176$ calories to remove. The final target is $1,760 - 176 = 1,584$ calories. Looking at the wrong answers: Choice (A) 1,540 likely results from calculation errors or applying both percentages incorrectly. Choice (C) 1,760 is the intermediate value after only the first reduction—this traps students who forget about the second 10% reduction. Choice (D) 1,980 represents applying only a 10% reduction to the original amount, missing the sequential nature entirely. The most common mistake is applying both percentages to the original amount (thinking 30% total reduction), but percentage reductions are cumulative and sequential. Always apply each new percentage to the most recent value, not the starting point. When you see multi-step percentage problems on the HESI, work through each step methodically and double-check that you're using the correct base amount for each calculation.
A pediatric medication dose is 15 mg/kg. The patient, who originally weighed 20 kg, has gained 10% of their body weight. What is the new total dose of the medication the patient should receive?
Answer: 330 mg Pediatric dosing calculations require you to account for the patient's current weight, not their original weight, since medication effectiveness depends on the body mass that needs treatment. Start by calculating the patient's new weight after the 10% gain. The original weight was 20 kg, so a 10% increase means: $20 \text{ kg} + (0.10 × 20 \text{ kg}) = 20 \text{ kg} + 2 \text{ kg} = 22 \text{ kg}$ Now apply the dosing formula using the current weight: $15 \text{ mg/kg} × 22 \text{ kg} = 330 \text{ mg}$ Looking at the wrong answers reveals common calculation errors. Choice A (30 mg) suggests someone multiplied the dose per kilogram (15 mg/kg) by only 2 kg—perhaps confusing the weight gain with the total weight. Choice B (300 mg) comes from using the original weight of 20 kg instead of the updated weight (15 mg/kg × 20 kg = 300 mg), which is a critical error since the patient's body mass has changed. Choice C (315 mg) appears to result from adding the weight gain incorrectly or making an arithmetic error in the final multiplication. The correct answer is D (330 mg) because it properly accounts for the patient's current body weight of 22 kg. Remember this key principle for HESI dosing questions: always use the patient's most current weight for calculations. Weight changes directly affect how much medication the body needs, so outdated measurements can lead to underdosing or overdosing. Double-check your weight calculations before moving to the dosing formula.
A patient's current weight is 170 pounds, which represents a 15% loss from their weight a year ago. What was the patient's approximate weight a year ago?
Answer: 200.0 lbs Weight loss percentage problems require you to work backwards from the current weight to find the original weight. When you see that a patient has lost 15% of their weight, this means their current weight represents 85% of their original weight. To solve this, set up the equation: Current weight = Original weight × (100% - 15%). Since 170 pounds represents 85% of the original weight, you can write: $170 = 0.85 × \text{Original weight}$ Solving for the original weight: $\text{Original weight} = \frac{170}{0.85} = 200 \text{ pounds}$ You can verify this: 15% of 200 pounds is 30 pounds, so 200 - 30 = 170 pounds ✓ Choice A (144.5 lbs) represents a common error where students subtract 15% of the current weight (170) from the current weight, calculating 170 - (0.15 × 170) = 144.5. This incorrectly assumes the current weight is the starting point. Choice B (147.8 lbs) is also less than the current weight, which is impossible since the patient lost weight from their original weight. Choice C (195.5 lbs) might result from incorrectly calculating 15% of 170 and adding it to 170, or from computational errors in the division. Remember this key principle: when someone loses a percentage of their weight, their current weight represents what's left after the loss. Always identify what percentage the current weight represents of the original, then divide accordingly. Weight loss problems are common on the HESI, so practice setting up these "percent of original" equations.
A medication's effectiveness rate increased from 72% to 81% after reformulation. A competing medication's effectiveness increased from 65% to 78%. Which medication had the greater percent increase in effectiveness, and by how much?
Answer: The competing medication by 7.5 percent First medication: percent increase = (81 - 72) ÷ 72 × 100 = 12.5%. Competing medication: percent increase = (78 - 65) ÷ 65 × 100 = 20.0%. The competing medication had a greater percent increase by 20.0% - 12.5% = 7.5 percent. Choice A confuses percentage points with percent increase. Choice C incorrectly calculates which medication had the greater increase. Choice D fails to recognize the different bases for calculation (72 vs 65).
A physical therapy clinic's patient volume changed as follows over three consecutive months: increased 25% in month 1, decreased 20% in month 2, and increased 10% in month 3. If they ended with 330 patients, how many patients did they have initially?
Answer: 300 patients initially When you encounter sequential percentage changes in healthcare administration problems, you need to work backwards from the final value to find the initial amount. Each percentage change creates a multiplier that you apply to track the patient volume through time. Let's call the initial number of patients $x$ and trace through each month. In month 1, a 25% increase means the volume becomes $1.25x$ . In month 2, a 20% decrease from that new level gives us $1.25x \times 0.80 = 1.00x$ . Finally, month 3's 10% increase results in $1.00x \times 1.10 = 1.10x = 330$ patients. Solving for $x$ : $x = \frac{330}{1.10} = 300$ patients initially. Choice A (250 patients) represents a common error where students might incorrectly calculate the net percentage change as +25% - 20% + 10% = +15%, then work backwards using 250 × 1.15 ≈ 288, which doesn't match the final value. Choice B (280 patients) likely results from arithmetic errors in the sequential calculations or confusion about which direction to apply the percentages. Choice C (275 patients) appears to stem from incorrectly handling the compounding effect of percentage changes, possibly by averaging values inappropriately. For percentage change problems on the HESI, always remember that each change builds on the previous result, not the original value. Set up your equation by multiplying all the change factors together, then work backwards from the final value to avoid calculation errors.
A medical clinic's patient satisfaction score is 92.4, following a 5% increase this year and a 10% increase the previous year. What was the clinic's approximate score two years ago?
Answer: 80.0 When you encounter percentage increase problems that work backwards through time, you need to reverse the process by dividing rather than multiplying. Think of this as "undoing" each increase step by step, starting from the current value. Let's work backwards from the current score of 92.4. This year there was a 5% increase, meaning the score at the start of this year was 100% and it grew to 105%. To find the previous value, divide by 1.05: $92.4 ÷ 1.05 = 88.0$ The previous year had a 10% increase, so that year's starting score grew from 100% to 110%. Again, divide to reverse this: $88.0 ÷ 1.10 = 80.0$ Therefore, the score two years ago was 80.0, making B correct. Looking at the wrong answers: A (79.0) likely results from calculation errors in the division process. C (80.3) suggests rounding errors or using approximate percentages instead of precise decimal calculations. D (87.8) represents a common trap - this would be the score if you only reversed one year's increase (just the 5%) instead of both years. The key mistake many students make is trying to subtract the percentage points directly (like 92.4 - 5 - 10 = 77.4) rather than understanding that percentage increases are multiplicative. When working backwards through percentage changes, always divide by (1 + percentage as decimal). Practice these step-by-step reversals, and always double-check by working forward to verify your answer.
A medical supply company offers a 15% discount for orders over $500, followed by an additional 8% discount for paying within 10 days. If a hospital's original order totaled $640, what is the overall percent decrease from the original price after both discounts are applied?
Answer: 21.8% First discount (15%): $640 × 0.85 = $544. Second discount (8% of the discounted price): $544 × 0.92 = $500.48. Overall percent decrease: ($640 - $500.48) ÷ $640 × 100 = $139.52 ÷ $640 × 100 = 21.8%. Choice A incorrectly adds the two percentages (15% + 8% = 23%). Choice C represents applying the second discount to the original price rather than the discounted price. Choice D results from calculation errors in the sequential discount application.
A patient's daily sodium intake was reduced from 3,000 mg to 2,400 mg. The following week, the intake was reduced again by the same percentage. What was the patient's sodium intake after the second reduction?
Answer: 1920 mg When you encounter percentage reduction problems in healthcare calculations, you're working with compound changes where each reduction is based on the new amount, not the original starting point. First, calculate the percentage reduction from the initial change: $\frac{3000 - 2400}{3000} = \frac{600}{3000} = 0.20 = 20\%$ For the second week, apply this same 20% reduction to the current intake of 2,400 mg: $2400 \times 0.20 = 480 \text{ mg reduction}$ Therefore: $2400 - 480 = 1920 \text{ mg}$ Answer C (1920 mg) is correct because it properly applies the percentage reduction to the adjusted amount from week one. Answer A (1800 mg) represents a common error where students might calculate 20% of the original 3,000 mg (600 mg) and subtract it twice: 3000 - 600 - 600 = 1800. This incorrectly treats both reductions as if they're based on the original amount. Answer B (1820 mg) likely results from calculation errors or incorrect percentage applications during the multi-step process. Answer D (2000 mg) might occur if you mistakenly subtract a flat 400 mg (the difference between 2400 and 2000) instead of calculating the proper percentage reduction. Study tip: In compound percentage problems, always apply each percentage change to the most recent value, not the original starting point. This pattern appears frequently in medication dosing and dietary modification questions on the HESI.
A patient's weight decreased from 180 pounds to 162 pounds over three months. What was the percentage decrease in the patient's weight?
Answer: 10% When you encounter percentage change problems on the HESI, you're applying a fundamental formula that appears frequently in healthcare calculations, from medication dosages to patient monitoring metrics. To find percentage decrease, use this formula: $\text{Percentage decrease} = \frac{\text{Original value} - \text{New value}}{\text{Original value}} \times 100$ Here, the patient's original weight was 180 pounds and the new weight is 162 pounds. First, calculate the actual decrease: 180 - 162 = 18 pounds. Then divide this decrease by the original weight: $\frac{18}{180} = 0.10$ . Finally, convert to percentage: 0.10 × 100 = 10%. Looking at the incorrect options: Choice (A) 9% represents a calculation error, likely from rounding too early or miscalculating the fraction. Choice (C) 11.1% occurs when students accidentally use the new weight (162) as the denominator instead of the original weight (180) - this gives you 18/162 ≈ 0.111. Choice (D) 18% is the trap answer where students report the absolute weight loss (18 pounds) as if it were already a percentage. The correct answer is (B) 10%. Study tip: Always use the original value as your denominator in percentage change calculations. A quick check: if someone loses 18 pounds from 180 pounds, that's roughly 1/10 of their body weight, which should immediately suggest 10%. This mental approximation can help you catch calculation errors on exam day.
A pharmacy's inventory management system shows that after a 20% price increase, a medication's sales volume decreased such that total revenue remained unchanged. What was the percent decrease in sales volume?
Answer: 16.67% decrease in volume When you encounter questions about price changes and sales volume where total revenue remains constant, you're working with inverse proportional relationships. The key insight is that if price goes up and revenue stays the same, volume must decrease proportionally. Let's set up the relationship mathematically. If original price is P and original volume is V, then original revenue = P × V. After changes: new revenue = (1.20P) × (new volume) = P × V. Solving for the new volume: (1.20P) × (new volume) = P × V, so new volume = V ÷ 1.20 = V ÷ (6/5) = V × (5/6) = 0.8333V. This means the new volume is 83.33% of the original volume, representing a decrease of 100% - 83.33% = 16.67%. Looking at the wrong answers: Choice A (25% decrease) represents a common error where students incorrectly assume that a 20% price increase requires a 25% volume decrease (since 1 ÷ 1.20 ≈ 0.80). Choice B (20% decrease) is the trap of assuming the percentage changes are equal, which would actually increase total revenue. Choice D (33.33% decrease) comes from confusing the relationship direction or making calculation errors. For HESI pharmacy calculations, remember that when price and volume changes result in constant revenue, use the formula: percent volume change = (1 ÷ price multiplier - 1) × 100%. This inverse relationship pattern appears frequently in healthcare economics questions.

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