Fraction Operations - ISEE Upper Level Mathematics Achievement

In a lab, a beaker holds $2\,1/3$ L; $5/6$ L is poured out. What volume remains?
Answer: $1\,1/2$ L This question tests ISEE Upper Level Mathematics Achievement skills: add, subtract, multiply, and divide fractions. Fractions are numbers that represent parts of a whole. Operations with fractions involve adding, subtracting, multiplying, and dividing these numbers while adhering to rules specific to fraction arithmetic. In the given scenario, students must apply these rules to solve a problem involving subtracting 5/6 L from 2 1/3 L of liquid in a beaker. The correct answer is choice A, 1 1/2 L, which accurately represents the result of converting to common denominators (2 1/3 = 2 2/6, then 2 2/6 - 5/6 = 1 3/6 = 1 1/2). Choice B (3 1/6) is incorrect due to adding instead of subtracting, a common mistake when students misread the operation. To assist students, encourage the practice of converting fractions to common denominators for addition and subtraction, and using reciprocal operations for division.
If $\frac{a}{b} = \frac{3}{7}$ and $\frac{c}{d} = \frac{2}{5}$ , what is the value of $\frac{a \cdot c}{b \cdot d}$ ?
Answer: $\frac{6}{35}$ When you see fractions being multiplied together, you can use the fundamental property that multiplying fractions means multiplying numerators together and denominators together: $\frac{a}{b} \cdot \frac{c}{d} = \frac{a \cdot c}{b \cdot d}$ . Since you're given that $\frac{a}{b} = \frac{3}{7}$ and $\frac{c}{d} = \frac{2}{5}$ , you can substitute these values directly into the multiplication: $\frac{a \cdot c}{b \cdot d} = \frac{3}{7} \cdot \frac{2}{5} = \frac{3 \cdot 2}{7 \cdot 5} = \frac{6}{35}$ . This matches choice A. Let's examine why the other answers are incorrect. Choice B gives $\frac{5}{12}$ , which might result from incorrectly adding the fractions instead of multiplying them, or from some other computational error. Choice C shows $\frac{1}{6}$ , which doesn't follow from any reasonable operation on the given fractions. Choice D presents $\frac{21}{10}$ , which you might get if you mistakenly flipped one of the fractions or cross-multiplied incorrectly. The key insight here is recognizing that $\frac{a \cdot c}{b \cdot d}$ is simply asking for the product of two fractions you already know. Remember that when multiplying fractions, you multiply straight across - numerator times numerator, denominator times denominator. Don't overthink these problems by trying to find individual values for a, b, c, and d when the given ratios are sufficient to solve directly.
A rectangular garden has length $\frac{5}{6}$ meters and width $\frac{3}{4}$ meters. If the garden is divided into plots each with area $\frac{1}{8}$ square meters, how many plots can be created?
Answer: 5 plots To find how many plots fit, divide the garden's area by the area of one plot. The garden's area is $\frac{5}{6} \times \frac{3}{4} = \frac{15}{24} = \frac{5}{8}$ square meters. Dividing by the plot area: $\frac{5}{8} \div \frac{1}{8} = \frac{5}{8} \times 8 = 5$ plots. An answer of 6 plots or 4 plots comes from an arithmetic slip in the area, such as simplifying $\frac{15}{24}$ incorrectly. An answer of 3 plots can come from adding the side lengths or from dividing a single side length by the plot area instead of the full area. The garden can be divided into 5 plots.
What is $\left(\frac{2}{3}\right)^2 \div \frac{8}{27}$ ?
Answer: $\frac{3}{2}$ This problem tests your ability to work with exponents and division of fractions. When you see division by a fraction, remember that dividing by a fraction is the same as multiplying by its reciprocal. First, calculate $\left(\frac{2}{3}\right)^2$ . When you square a fraction, you square both the numerator and denominator: $\left(\frac{2}{3}\right)^2 = \frac{2^2}{3^2} = \frac{4}{9}$ . Now you need to compute $\frac{4}{9} \div \frac{8}{27}$ . To divide by a fraction, multiply by its reciprocal: $\frac{4}{9} \times \frac{27}{8}$ . Multiply the fractions: $\frac{4 \times 27}{9 \times 8} = \frac{108}{72}$ . Simplify by finding the greatest common factor. Both 108 and 72 are divisible by 36: $\frac{108}{72} = \frac{108 \div 36}{72 \div 36} = \frac{3}{2}$ . Looking at the wrong answers: Choice A ( $\frac{1}{2}$ ) likely results from incorrectly multiplying instead of dividing, or making arithmetic errors. Choice C ( $\frac{2}{3}$ ) might come from confusing the original fraction with the final answer. Choice D ( $\frac{4}{9}$ ) is what you get if you stop after squaring $\frac{2}{3}$ and forget to complete the division. The correct answer is B: $\frac{3}{2}$ . Strategy tip: When dividing fractions, always convert to multiplication by the reciprocal immediately. This prevents confusion and makes the arithmetic cleaner. Also, look for opportunities to simplify before multiplying to make calculations easier.
A student reads $\frac{2}{5}$ of a book on Monday and $\frac{1}{4}$ of the remaining pages on Tuesday. What fraction of the entire book has the student read after Tuesday?
Answer: $\frac{11}{20}$ When you encounter problems involving sequential fractions of a whole, the key is carefully tracking what each fraction refers to. The second fraction operates on what remains after the first action, not on the original whole. Let's work through this step-by-step. On Monday, the student reads $\frac{2}{5}$ of the entire book. This means $\frac{3}{5}$ of the book remains unread after Monday. On Tuesday, the student reads $\frac{1}{4}$ of the remaining pages. Since $\frac{3}{5}$ of the book remained, Tuesday's reading equals $\frac{1}{4} \times \frac{3}{5} = \frac{3}{20}$ of the entire book. The total fraction read after both days is: $\frac{2}{5} + \frac{3}{20}$ . Converting to a common denominator: $\frac{8}{20} + \frac{3}{20} = \frac{11}{20}$ . This confirms answer C. Looking at the wrong answers: Answer A ( $\frac{13}{20}$ ) likely comes from incorrectly adding $\frac{2}{5} + \frac{1}{4}$ directly, giving $\frac{8}{20} + \frac{5}{20} = \frac{13}{20}$ . This mistake ignores that Tuesday's fraction applies only to remaining pages. Answer B ( $\frac{3}{5}$ ) represents only Monday's reading. Answer D ( $\frac{7}{10}$ ) might result from computational errors when finding common denominators. Remember: when fractions in word problems refer to "remaining" or "leftover" amounts, always multiply by what's actually left, not the original whole. Draw a picture or use concrete numbers if the abstract fractions feel confusing.
A jar contains red and blue marbles in the ratio $3:5$ . If there are 15 red marbles, how many blue marbles are there?
Answer: 25 marbles When you encounter ratio problems, you're working with proportional relationships between quantities. The key insight is that ratios tell you the relative sizes of groups, and you can use this information to find actual quantities when given one piece of the puzzle. The ratio $3:5$ means that for every 3 red marbles, there are 5 blue marbles. Since you know there are 15 red marbles, you need to figure out what multiple of 3 gives you 15. Dividing: $15 ÷ 3 = 5$ . This means the ratio has been scaled up by a factor of 5. Therefore, the blue marbles must also be scaled up by the same factor: $5 × 5 = 25$ blue marbles. You can verify this by checking that $15:25$ simplifies to $3:5$ (dividing both by 5). Looking at the wrong answers: Choice A (20 marbles) would create a ratio of $15:20$ , which simplifies to $3:4$ , not $3:5$ . Choice C (18 marbles) gives $15:18$ , which simplifies to $5:6$ - the ratio is actually flipped and incorrect. Choice D (30 marbles) creates $15:30$ , simplifying to $1:2$ , which is completely different from the given ratio. The correct answer is B) 25 marbles. Strategy tip: In ratio problems, always find the scaling factor first by dividing the known quantity by its corresponding ratio number, then apply that same factor to find the unknown quantity. This systematic approach prevents calculation errors.
What is the reciprocal of $\frac{2}{3} \div \frac{4}{9}$ ?
Answer: $\frac{2}{3}$ This question tests your ability to work with fraction division and reciprocals in sequence. When you see a complex fraction expression followed by "find the reciprocal," break it down step by step rather than trying to do everything at once. First, you need to evaluate $\frac{2}{3} \div \frac{4}{9}$ . Remember that dividing by a fraction means multiplying by its reciprocal: $\frac{2}{3} \div \frac{4}{9} = \frac{2}{3} \times \frac{9}{4}$ . Multiplying across gives you $\frac{2 \times 9}{3 \times 4} = \frac{18}{12}$ . This simplifies to $\frac{3}{2}$ when you divide both numerator and denominator by 6. Now you need the reciprocal of $\frac{3}{2}$ , which is $\frac{2}{3}$ . This makes choice A correct. Choice B ( $\frac{3}{2}$ ) is the result of the division but not its reciprocal - a common error when students forget the final step. Choice C ( $\frac{1}{2}$ ) likely comes from incorrectly calculating the original division, possibly by multiplying $\frac{2}{3} \times \frac{4}{9}$ instead of dividing. Choice D ( $\frac{9}{8}$ ) might result from flipping the wrong fraction during the division step or making arithmetic errors in the multiplication. The key strategy here is to work systematically: first complete the division operation, then find the reciprocal of that result. Don't try to take shortcuts by looking for reciprocals earlier in the process, as this often leads to confusion about which fraction to flip.
A lab protocol requires $5/4$ g salt; $1/2$ g is removed. What mass remains?
Answer: $3/4$ g This question tests ISEE Upper Level Mathematics Achievement skills: add, subtract, multiply, and divide fractions. Fractions are numbers that represent parts of a whole. Operations with fractions involve adding, subtracting, multiplying, and dividing these numbers while adhering to rules specific to fraction arithmetic. In the given scenario, students must apply these rules to solve a problem involving subtracting 1/2 g from 5/4 g of salt in a lab protocol. The correct answer is choice B, 3/4 g, which accurately represents the result of finding common denominators and subtracting (5/4 - 1/2 = 5/4 - 2/4 = 3/4). Choice A (3/8) is incorrect due to improper subtraction technique, a common mistake when students subtract numerators and denominators separately. To assist students, encourage the practice of converting fractions to common denominators for addition and subtraction, and using reciprocal operations for division.
A car travels $\frac{2}{3}$ of a 240-mile journey in the first day. On the second day, it travels $\frac{3}{4}$ of the remaining distance. How many miles are left to travel?
Answer: 20 miles This is a multi-step fraction problem that requires you to track remaining distances after each day of travel. The key is working through each day systematically and keeping track of what's left after each portion is completed. On the first day, the car travels $\frac{2}{3}$ of 240 miles. Calculate this: $\frac{2}{3} \times 240 = 160$ miles. This means $240 - 160 = 80$ miles remain after day one. On the second day, the car travels $\frac{3}{4}$ of the remaining 80 miles. Calculate this: $\frac{3}{4} \times 80 = 60$ miles. After the second day, $80 - 60 = 20$ miles are left to travel. Looking at the wrong answers: Choice B (40 miles) is what you'd get if you mistakenly calculated half of the remaining distance after day one instead of $\frac{3}{4}$ . Choice C (30 miles) results from incorrectly finding $\frac{1}{4}$ of the remaining distance and subtracting it from 50 instead of 80. Choice D (60 miles) is the distance traveled on day two, not what remains—a common error when students confuse "distance traveled" with "distance remaining." The correct answer is A: 20 miles. When tackling multi-step fraction problems, always write down what remains after each step rather than trying to do all calculations mentally. This prevents you from mixing up intermediate results with your final answer, which is a frequent trap on these types of problems.
A tile strip is $3\,3/4$ ft long; each tile is $5/8$ ft. Divide to find tiles needed.
Answer: $6$ tiles This question tests ISEE Upper Level Mathematics Achievement skills: add, subtract, multiply, and divide fractions. Fractions are numbers that represent parts of a whole. Operations with fractions involve adding, subtracting, multiplying, and dividing these numbers while adhering to rules specific to fraction arithmetic. In the given scenario, students must apply these rules to solve a problem involving dividing 3 3/4 ft by 5/8 ft to find the number of tiles needed. The correct answer is choice B, 6 tiles, which accurately represents the result of dividing fractions (3 3/4 = 15/4, then 15/4 ÷ 5/8 = 15/4 × 8/5 = 120/20 = 6). Choice A (2 11/24) is incorrect due to multiplying instead of dividing, a common mistake when students forget to use the reciprocal in division. To assist students, encourage the practice of converting fractions to common denominators for addition and subtraction, and using reciprocal operations for division.
If $\frac{2x-1}{3} = \frac{5}{6}$ , what is the value of $x$ ?
Answer: $\frac{7}{4}$ When you encounter an equation with a fraction equal to another fraction, your goal is to isolate the variable by eliminating the fraction first. This is a linear equation that requires careful algebraic manipulation. To solve $\frac{2x-1}{3} = \frac{5}{6}$ , start by eliminating the fraction on the left side. Multiply both sides by 3: $2x - 1 = 3 \cdot \frac{5}{6} = \frac{15}{6} = \frac{5}{2}$ Now you have $2x - 1 = \frac{5}{2}$ . Add 1 to both sides: $2x = \frac{5}{2} + 1 = \frac{5}{2} + \frac{2}{2} = \frac{7}{2}$ Finally, divide both sides by 2: $x = \frac{7}{2} \div 2 = \frac{7}{2} \cdot \frac{1}{2} = \frac{7}{4}$ This confirms that answer choice B is correct. Looking at the wrong answers: Choice A ( $\frac{5}{4}$ ) likely results from incorrectly adding fractions or making an arithmetic error when combining $\frac{5}{2} + 1$ . Choice C ( $\frac{3}{2}$ ) could come from forgetting to divide by 2 in the final step, stopping at $2x = \frac{7}{2}$ and misreading this as the final answer. Choice D ( $\frac{11}{12}$ ) suggests errors in fraction arithmetic, possibly when multiplying $3 \cdot \frac{5}{6}$ . Study tip: Always work systematically with fraction equations—eliminate fractions first, then use inverse operations. Double-check your fraction arithmetic, especially when adding fractions with different denominators.
A lab uses $3\,1/5$ mL solution; $4/5$ mL is transferred. What is the remaining volume?
Answer: $2\,2/5$ mL This question tests ISEE Upper Level Mathematics Achievement skills: add, subtract, multiply, and divide fractions. Fractions are numbers that represent parts of a whole. Operations with fractions involve adding, subtracting, multiplying, and dividing these numbers while adhering to rules specific to fraction arithmetic. In the given scenario, students must apply these rules to solve a problem involving subtracting 4/5 mL from 3 1/5 mL of solution. The correct answer is choice A, 2 2/5 mL, which accurately represents the result of converting to common denominators and subtracting (3 1/5 - 4/5 = 3 1/5 - 4/5 = 2 2/5). Choice C (1 3/5) is incorrect due to improper subtraction technique, a common mistake when students subtract whole numbers and fractions separately without regrouping. To assist students, encourage the practice of converting fractions to common denominators for addition and subtraction, and using reciprocal operations for division.
If $\frac{x}{y} = \frac{4}{5}$ and $x + y = 27$ , what is the value of $x - y$ ?
Answer: $-3$ When you encounter a system with both a ratio and a sum, you can use substitution to solve for individual variables efficiently. Since $\frac{x}{y} = \frac{4}{5}$ , you know that $x = \frac{4y}{5}$ . Now substitute this into the second equation: $x + y = 27$ becomes $\frac{4y}{5} + y = 27$ . To solve this, convert $y$ to fifths: $\frac{4y}{5} + \frac{5y}{5} = 27$ , which gives you $\frac{9y}{5} = 27$ . Multiply both sides by 5: $9y = 135$ , so $y = 15$ . With $y = 15$ , you can find $x$ : $x = \frac{4(15)}{5} = 12$ . Therefore, $x - y = 12 - 15 = -3$ . Looking at the answer choices: (A) -3 is correct. (B) 3 represents the absolute value of the correct answer - a common trap when students forget that $x < y$ in this problem, making the difference negative. (C) -6 and (D) 6 might result from calculation errors, such as incorrectly setting up the substitution or making arithmetic mistakes when combining fractions. Strategy tip: When working with ratio and sum problems, always substitute the ratio relationship into the sum equation first. Also, pay attention to the order in subtraction problems - since the ratio $\frac{4}{5}$ tells you that $x$ is smaller than $y$ , expect $x - y$ to be negative.
A swimming pool is $\frac{3}{4}$ full. After draining $\frac{1}{5}$ of the water currently in the pool, what fraction of the pool's total capacity is occupied by water?
Answer: $\frac{3}{5}$ When you encounter fraction problems involving sequential operations, work step-by-step and keep track of what each fraction refers to—whether it's a fraction of the total capacity or a fraction of the current amount. Start with the pool at $\frac{3}{4}$ full. Now you're draining $\frac{1}{5}$ of the water currently in the pool, not $\frac{1}{5}$ of the total capacity. This means you're removing $\frac{1}{5} \times \frac{3}{4} = \frac{3}{20}$ of the pool's total capacity. After draining, the remaining water is: $\frac{3}{4} - \frac{3}{20}$ . To subtract these fractions, find a common denominator: $\frac{15}{20} - \frac{3}{20} = \frac{12}{20} = \frac{3}{5}$ . Looking at the wrong answers: Choice A ( $\frac{11}{20}$ ) likely comes from incorrectly calculating $\frac{3}{4} - \frac{1}{5}$ directly, ignoring that you drain $\frac{1}{5}$ of the current water, not the total capacity. Choice C ( $\frac{7}{10}$ ) might result from adding instead of subtracting somewhere in the calculation. Choice D ( $\frac{9}{20}$ ) could come from mistakenly calculating $\frac{3}{4} \times \frac{4}{5}$ incorrectly or making an arithmetic error with the common denominators. The key strategy for these problems is to carefully read what each fraction represents. When you see "drain $\frac{1}{5}$ of the water currently in the pool," multiply that fraction by the current amount, don't subtract it directly from the total capacity. Always identify your reference point before performing operations.
A machine produces $\frac{5}{8}$ of its daily quota in the morning and $\frac{1}{3}$ of its daily quota in the afternoon. What fraction of the daily quota remains to be produced?
Answer: $\frac{1}{24}$ When you encounter fraction problems involving parts of a whole, you need to add or subtract the fractions to find what remains. This question asks you to find how much of the daily quota is left after morning and afternoon production. First, add the fractions representing what was already produced. The machine produces $\frac{5}{8}$ in the morning and $\frac{1}{3}$ in the afternoon. To add these fractions, you need a common denominator. The least common multiple of 8 and 3 is 24. Convert each fraction: $\frac{5}{8} = \frac{15}{24}$ and $\frac{1}{3} = \frac{8}{24}$ Adding them: $\frac{15}{24} + \frac{8}{24} = \frac{23}{24}$ Since the total daily quota represents 1 whole (or $\frac{24}{24}$ ), subtract what was produced from the total: $\frac{24}{24} - \frac{23}{24} = \frac{1}{24}$ This confirms answer A is correct. Looking at the wrong answers: B) $\frac{7}{24}$ might result from incorrectly subtracting $\frac{8}{24}$ from $\frac{15}{24}$ instead of adding them first. C) $\frac{5}{24}$ could come from subtracting only the afternoon production from the morning production. D) $\frac{1}{8}$ might result from using the wrong common denominator or computational errors. Remember: in "parts of a whole" problems, always check that your answer makes sense. Since most of the quota was already produced ( $\frac{23}{24}$ ), only a tiny fraction should remain, making $\frac{1}{24}$ reasonable.
Simplify: $\frac{\frac{3}{4} + \frac{1}{8}}{\frac{5}{6} - \frac{1}{3}}$
Answer: $\frac{7}{4}$ When you encounter a complex fraction (a fraction containing other fractions), your goal is to simplify both the numerator and denominator separately, then divide. Let's start with the numerator: $\frac{3}{4} + \frac{1}{8}$ . To add fractions, you need a common denominator. Since 8 is a multiple of 4, convert $\frac{3}{4}$ to eighths: $\frac{3}{4} = \frac{6}{8}$ . Now add: $\frac{6}{8} + \frac{1}{8} = \frac{7}{8}$ . For the denominator: $\frac{5}{6} - \frac{1}{3}$ . The common denominator is 6, so convert $\frac{1}{3}$ to sixths: $\frac{1}{3} = \frac{2}{6}$ . Now subtract: $\frac{5}{6} - \frac{2}{6} = \frac{3}{6} = \frac{1}{2}$ . Your complex fraction is now $\frac{\frac{7}{8}}{\frac{1}{2}}$ . To divide by a fraction, multiply by its reciprocal: $\frac{7}{8} \times \frac{2}{1} = \frac{14}{8} = \frac{7}{4}$ . This confirms answer A. Answer B ( $\frac{21}{8}$ ) results from incorrectly multiplying the numerator by 3 instead of properly finding the common denominator. Answer C ( $\frac{5}{3}$ ) comes from calculation errors in both the numerator and denominator operations. Answer D ( $\frac{7}{2}$ ) occurs when you forget to reduce $\frac{3}{6}$ to $\frac{1}{2}$ in the denominator, leading to $\frac{7}{8} \div \frac{3}{6} = \frac{7}{8} \times \frac{6}{3} = \frac{7}{4} \times \frac{3}{2}$ . Remember: always simplify fractions completely at each step, and double-check your common denominators before adding or subtracting.
A rope $\frac{7}{8}$ meters long is cut into pieces, each $\frac{1}{6}$ meters long. How many complete pieces can be made, and what length of rope remains?
Answer: 5 pieces with $\frac{1}{24}$ meters remaining When you encounter a word problem involving division of fractions, you're essentially finding how many times one quantity fits into another, plus any remainder. To find how many complete pieces you can make, divide the total rope length by the length of each piece: $\frac{7}{8} ÷ \frac{1}{6}$ . When dividing fractions, multiply by the reciprocal: $\frac{7}{8} × \frac{6}{1} = \frac{42}{8} = \frac{21}{4} = 5\frac{1}{4}$ . Since you can only make complete pieces, you get 5 pieces. To find the remaining rope, multiply the number of complete pieces by the piece length, then subtract from the original length: $5 × \frac{1}{6} = \frac{5}{6}$ . Now calculate $\frac{7}{8} - \frac{5}{6}$ . Using the common denominator 24: $\frac{21}{24} - \frac{20}{24} = \frac{1}{24}$ . Therefore, answer A is correct. Choice B incorrectly assumes only 4 complete pieces can be made, which underestimates the division result. Choice C correctly identifies 5 pieces but miscalculates the remainder—this likely comes from arithmetic errors in fraction subtraction. Choice D combines both errors: wrong number of pieces and wrong remainder calculation. Remember that division word problems with fractions have two parts: the whole number tells you complete units, while the fractional part helps you calculate the remainder. Always convert mixed numbers properly and double-check your fraction arithmetic using common denominators.
A water tank is $\frac{7}{8}$ full. After using $\frac{1}{3}$ of the water currently in the tank, what fraction of the tank's total capacity remains?
Answer: $\frac{7}{12}$ This problem tests your ability to work with fractions of fractions — a key skill where you need to carefully track what each fraction refers to. Start by identifying what you know: the tank is $\frac{7}{8}$ full, and you use $\frac{1}{3}$ of the water currently in the tank. The key insight is that $\frac{1}{3}$ refers to one-third of the water that's actually there, not one-third of the tank's total capacity. To find how much water is used, multiply: $\frac{1}{3} \times \frac{7}{8} = \frac{7}{24}$ of the tank's total capacity is removed. The remaining water is: $\frac{7}{8} - \frac{7}{24}$ . To subtract these fractions, find a common denominator of 24: $\frac{21}{24} - \frac{7}{24} = \frac{14}{24} = \frac{7}{12}$ . Looking at the wrong answers: Choice B ( $\frac{5}{8}$ ) comes from incorrectly thinking you remove $\frac{1}{3}$ from $\frac{7}{8}$ by subtracting the numerators: $7-1=6$ , then simplifying $\frac{6}{8}$ to $\frac{3}{4}$ — but this isn't among the choices, leading to further errors. Choice C ( $\frac{13}{24}$ ) results from adding instead of subtracting during the calculation. Choice D ( $\frac{7}{24}$ ) is the amount of water removed, not the amount remaining. When you see "fraction of fraction" problems, always identify what the second fraction refers to — is it a fraction of the total capacity or a fraction of what's currently there? This distinction is crucial for setting up your calculation correctly.
A construction project is $\frac{2}{3}$ complete. If $\frac{3}{8}$ of the remaining work can be finished this week, what fraction of the entire project will be completed by the end of the week?
Answer: $\frac{19}{24}$ When you encounter multi-step fraction problems involving "remaining work," break them down systematically by tracking what's completed versus what's left to do. Start with what you know: $\frac{2}{3}$ of the project is already complete, so the remaining work is $1 - \frac{2}{3} = \frac{1}{3}$ of the total project. This week, $\frac{3}{8}$ of that remaining $\frac{1}{3}$ will be finished. To find what fraction of the entire project this represents, multiply: $\frac{3}{8} \times \frac{1}{3} = \frac{3}{24} = \frac{1}{8}$ . By the end of the week, the total completed work will be: $\frac{2}{3} + \frac{1}{8}$ . To add these fractions, find a common denominator of 24: $\frac{2}{3} = \frac{16}{24}$ and $\frac{1}{8} = \frac{3}{24}$ . Therefore: $\frac{16}{24} + \frac{3}{24} = \frac{19}{24}$ . Choice A ( $\frac{3}{4}$ ) incorrectly assumes you complete $\frac{3}{4}$ of the total project this week. Choice B ( $\frac{7}{8}$ ) results from mistakenly adding $\frac{2}{3} + \frac{3}{8}$ incorrectly. Choice C ( $\frac{17}{24}$ ) comes from the common error of adding $\frac{2}{3} + \frac{3}{8}$ with the right denominator but wrong arithmetic: $\frac{16}{24} + \frac{9}{24}$ instead of recognizing that $\frac{3}{8}$ applies only to the remaining work. The answer is D ( $\frac{19}{24}$ ). Study tip: Always identify what the fraction applies to—the whole project or just the remaining portion—before performing calculations.
What is the value of $\frac{5}{6} \div \frac{2}{9} - \frac{1}{4}$ ?
Answer: $\frac{7}{2}$ Follow the order of operations: divide first, then subtract. To divide by a fraction, multiply by its reciprocal: $\frac{5}{6} \div \frac{2}{9} = \frac{5}{6} \times \frac{9}{2} = \frac{45}{12} = \frac{15}{4}$ . Then subtract: $\frac{15}{4} - \frac{1}{4} = \frac{14}{4} = \frac{7}{2}$ . A quick estimate catches the wrong answers. The quotient $\frac{15}{4}$ is $3\frac{3}{4}$ , and taking away $\frac{1}{4}$ leaves $3\frac{1}{2}$ . Values such as $\frac{31}{12}$ , $\frac{7}{3}$ , and $\frac{23}{12}$ are all less than $3$ , so each one reflects a slip in the division or the subtraction. The value is $\frac{7}{2}$ .

Start this quiz