Mixed-Number Problems

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ISEE Upper Level: Mathematics Achievement › Mixed-Number Problems

Questions 1 - 10
1

Tom's morning jog consists of three segments: $$2\frac{1}{6}$$ miles uphill, $$1\frac{3}{4}$$ miles on flat ground, and $$1\frac{5}{12}$$ miles downhill. What is the total distance of his jog?

$$4\frac{1}{3}$$ miles

$$5\frac{1}{3}$$ miles

$$6\frac{1}{4}$$ miles

$$5\frac{7}{12}$$ miles

Explanation

This question tests your ability to add mixed numbers with different denominators - a key skill for fraction arithmetic on the ISEE.

To find the total distance, you need to add $$2\frac{1}{6} + 1\frac{3}{4} + 1\frac{5}{12}$$. Start by adding the whole numbers: $$2 + 1 + 1 = 4$$. Next, add the fractions: $$\frac{1}{6} + \frac{3}{4} + \frac{5}{12}$$.

To add fractions, you need a common denominator. The least common multiple of 6, 4, and 12 is 12. Convert each fraction: $$\frac{1}{6} = \frac{2}{12}$$, $$\frac{3}{4} = \frac{9}{12}$$, and $$\frac{5}{12} = \frac{5}{12}$$.

Now add: $$\frac{2}{12} + \frac{9}{12} + \frac{5}{12} = \frac{16}{12} = 1\frac{4}{12} = 1\frac{1}{3}$$

Combining with the whole numbers: $$4 + 1\frac{1}{3} = 5\frac{1}{3}$$ miles, which is choice B.

Choice A ($$4\frac{1}{3}$$) likely results from forgetting to add one of the whole numbers. Choice C ($$5\frac{7}{12}$$) probably comes from incorrectly adding the fractions without converting to a common denominator first. Choice D ($$6\frac{1}{4}$$) suggests an error in finding the common denominator or adding the whole numbers incorrectly.

Remember: when adding mixed numbers, always find a common denominator for the fractions first, then simplify your final answer. Double-check by ensuring your result makes sense given the original values.

2

A carpenter cuts a $$10\frac{1}{2}$$-foot board into pieces that are each $$1\frac{3}{4}$$ feet long. How many complete pieces can be cut?

$$6$$ pieces

$$7$$ pieces

$$5$$ pieces

$$8$$ pieces

Explanation

When you encounter a word problem asking "how many complete pieces," you're dealing with a division problem where you need to find the whole number quotient, ignoring any remainder.

To solve this, divide the total length by the length of each piece: $$10\frac{1}{2} ÷ 1\frac{3}{4}$$. First, convert both mixed numbers to improper fractions. $$10\frac{1}{2} = \frac{21}{2}$$ and $$1\frac{3}{4} = \frac{7}{4}$$.

Now divide: $$\frac{21}{2} ÷ \frac{7}{4} = \frac{21}{2} × \frac{4}{7} = \frac{84}{14} = 6$$. Since this division results in exactly 6 with no remainder, the carpenter can cut exactly 6 complete pieces.

Looking at the wrong answers: Choice A (5 pieces) likely comes from rounding down unnecessarily or making an arithmetic error in the division. Choice C (7 pieces) might result from incorrectly adding the leftover fraction instead of ignoring it, or from conversion errors when working with the mixed numbers. Choice D (8 pieces) represents a significant calculation error, possibly from incorrectly converting the mixed numbers or misunderstanding the division process entirely.

The key insight is recognizing that "complete pieces" means you only count whole pieces—any leftover material that's shorter than $$1\frac{3}{4}$$ feet doesn't count as a complete piece. Always convert mixed numbers to improper fractions before dividing, and remember that division by a fraction means multiplying by its reciprocal.

3

A recipe calls for $$2\frac{3}{4}$$ cups of flour. Maria has already added $$1\frac{5}{8}$$ cups of flour to her mixing bowl. How much more flour does she need to add?

$$1\frac{3}{8}$$ cups

$$\frac{9}{8}$$ cups

$$4\frac{3}{8}$$ cups

$$1\frac{1}{8}$$ cups

Explanation

When you encounter mixed number subtraction problems, you need to find the difference between two quantities. Here, you're looking for how much more flour Maria needs: the recipe amount minus what she's already added.

Set up the subtraction: $$2\frac{3}{4} - 1\frac{5}{8}$$. Since the fractions have different denominators, convert to a common denominator first. The least common denominator of 4 and 8 is 8, so convert $$2\frac{3}{4}$$ to eighths: $$2\frac{3}{4} = 2\frac{6}{8}$$.

Now subtract: $$2\frac{6}{8} - 1\frac{5}{8}$$. Since $$\frac{6}{8} > \frac{5}{8}$$, you can subtract directly: $$(2-1) + (\frac{6}{8} - \frac{5}{8}) = 1\frac{1}{8}$$.

Looking at the wrong answers: Choice B ($$1\frac{3}{8}$$) likely comes from incorrectly adding the numerators instead of subtracting ($$\frac{6}{8} + \frac{5}{8} = \frac{11}{8} = 1\frac{3}{8}$$, then subtracting 1). Choice C ($$\frac{9}{8}$$) might result from subtracting only the whole numbers and adding the fractions. Choice D ($$4\frac{3}{8}$$) comes from adding the original amounts instead of subtracting.

Study tip: Always double-check your work by adding your answer back to what Maria already added. Here: $$1\frac{1}{8} + 1\frac{5}{8} = 2\frac{6}{8} = 2\frac{3}{4}$$ ✓. This confirms you need $$1\frac{1}{8}$$ cups more flour, making A correct.

4

A carpenter needs to cut a board that is $$8\frac{1}{3}$$ feet long into pieces that are each $$1\frac{2}{9}$$ feet long. How many complete pieces can be cut from the board?

$$7$$ pieces

$$9$$ pieces

$$6$$ pieces

$$8$$ pieces

Explanation

When you encounter a word problem asking "how many complete pieces," you're dealing with a division problem where you need to find how many times one quantity fits into another, then consider only whole pieces.

To solve this, divide the total board length by the length of each piece: $$8\frac{1}{3} \div 1\frac{2}{9}$$. First, convert both mixed numbers to improper fractions. For $$8\frac{1}{3}$$: multiply $$8 \times 3 = 24$$, then add $$1$$ to get $$\frac{25}{3}$$. For $$1\frac{2}{9}$$: multiply $$1 \times 9 = 9$$, then add $$2$$ to get $$\frac{11}{9}$$.

Now divide: $$\frac{25}{3} \div \frac{11}{9} = \frac{25}{3} \times \frac{9}{11} = \frac{225}{33}$$. Simplify by dividing both numerator and denominator by $$3$$: $$\frac{75}{11} = 6\frac{9}{11}$$.

Since the carpenter can only cut complete pieces, you take the whole number part: $$6$$ complete pieces, with some board left over. Wait—this suggests answer (A), but let me recalculate. $$\frac{225}{33} = \frac{75}{11} = 6.818...$$ Actually, this gives us $$6$$ complete pieces, making (A) seem correct.

However, let me verify: $$6 \times 1\frac{2}{9} = 6 \times \frac{11}{9} = \frac{66}{9} = 7\frac{3}{9}$$ feet used, leaving $$8\frac{1}{3} - 7\frac{3}{9} = \frac{25}{3} - \frac{66}{9} = \frac{75-66}{9} = 1$$ foot remaining. Since $$1 > \frac{11}{9}$$, there's enough for one more piece, giving us $$7$$ complete pieces total.

(A) stops at $$6$$ pieces, missing the seventh possible piece. (C) and (D) overestimate what can fit.

Always double-check division problems by multiplying back and seeing if there's enough remainder for another complete piece.

5

Emma drinks $$1\frac{3}{8}$$ liters of water in the morning and $$2\frac{5}{6}$$ liters in the afternoon. Her daily goal is $$5$$ liters. How much more water does she need to drink to reach her goal?

$$4\frac{5}{24}$$ liters

$$1\frac{5}{24}$$ liters

$$9\frac{5}{24}$$ liters

$$\frac{19}{24}$$ liters

Explanation

When you encounter word problems involving mixed numbers and fractions, you need to add what's consumed and subtract from the total goal to find what's remaining.

First, find how much water Emma drank total by adding $$1\frac{3}{8} + 2\frac{5}{6}$$. To add mixed numbers, you need a common denominator. The LCD of 8 and 6 is 24.

Convert to equivalent fractions: $$1\frac{3}{8} = 1\frac{9}{24}$$ and $$2\frac{5}{6} = 2\frac{20}{24}$$

Adding: $$1\frac{9}{24} + 2\frac{20}{24} = 3\frac{29}{24} = 4\frac{5}{24}$$ liters total consumed.

Now subtract from her 5-liter goal: $$5 - 4\frac{5}{24} = 4\frac{24}{24} - 4\frac{5}{24} = \frac{19}{24}$$ liters needed.

Looking at the wrong answers: Answer B ($$1\frac{5}{24}$$) likely comes from incorrectly subtracting just one of the amounts from 5 instead of their sum. Answer C ($$4\frac{5}{24}$$) is actually the total amount Emma already drank, not what she still needs - this represents confusing the intermediate step with the final answer. Answer D ($$9\frac{5}{24}$$) appears to come from adding all three numbers (morning + afternoon + goal) rather than using proper subtraction.

The correct answer is A: $$\frac{19}{24}$$ liters.

Study tip: In "how much more" problems, always add up what's already done first, then subtract from the target. Write out each step clearly to avoid mixing up intermediate calculations with your final answer.

6

A fabric store sells ribbon by the yard. Mrs. Johnson buys $$4\frac{2}{3}$$ yards of red ribbon and $$3\frac{1}{4}$$ yards of blue ribbon. She uses $$2\frac{5}{12}$$ yards for a project. How much ribbon does she have left?

$$7\frac{11}{12}$$ yards

$$5\frac{1}{3}$$ yards

$$5\frac{1}{2}$$ yards

$$10\frac{1}{4}$$ yards

Explanation

This problem tests your ability to work with mixed numbers through addition and subtraction - a key skill for fraction operations. When you see mixed numbers in word problems, you'll need to convert them to improper fractions or find a common denominator to perform the calculations accurately.

First, find the total ribbon Mrs. Johnson bought by adding $$4\frac{2}{3} + 3\frac{1}{4}$$. To add these mixed numbers, you need a common denominator. The LCD of 3 and 4 is 12: $$4\frac{8}{12} + 3\frac{3}{12} = 7\frac{11}{12}$$ yards total.

Next, subtract the amount used: $$7\frac{11}{12} - 2\frac{5}{12}$$. Since both fractions have the same denominator, subtract directly: $$7\frac{11}{12} - 2\frac{5}{12} = 5\frac{6}{12} = 5\frac{1}{2}$$ yards remaining.

Looking at the wrong answers: B) $$5\frac{1}{3}$$ results from incorrectly simplifying $$\frac{6}{12}$$ as $$\frac{1}{3}$$ instead of $$\frac{1}{2}$$. C) $$7\frac{11}{12}$$ is the total ribbon purchased before subtracting what was used - this catches students who forget the final subtraction step. D) $$10\frac{1}{4}$$ comes from adding all three quantities instead of adding the first two and subtracting the third.

The correct answer is A) $$5\frac{1}{2}$$ yards.

Study tip: In multi-step fraction problems, always double-check that you're performing the right operations in the correct order, and remember to reduce fractions to lowest terms in your final answer.

7

A recipe for trail mix calls for $$1\frac{1}{2}$$ cups of nuts for every $$\frac{3}{4}$$ cup of dried fruit. If Sarah wants to use $$3$$ cups of dried fruit, how many cups of nuts will she need?

$$4\frac{3}{4}$$ cups

$$4\frac{1}{2}$$ cups

$$2\frac{1}{4}$$ cups

$$6$$ cups

Explanation

This is a proportional reasoning problem where you need to scale up a recipe. When you see questions about recipes or mixing ratios, look for the relationship between ingredients and use it to find unknown quantities.

The recipe gives you a ratio: $$1\frac{1}{2}$$ cups of nuts for every $$\frac{3}{4}$$ cup of dried fruit. To find how many cups of nuts Sarah needs for 3 cups of dried fruit, set up a proportion. First, determine the scaling factor: how many times larger is 3 cups compared to $$\frac{3}{4}$$ cup? Divide $$3 \div \frac{3}{4} = 3 \times \frac{4}{3} = 4$$. So Sarah is making 4 times the original recipe. Therefore, she needs $$4 \times 1\frac{1}{2} = 4 \times \frac{3}{2} = 6$$ cups of nuts.

Choice A ($$2\frac{1}{4}$$ cups) represents incorrectly multiplying $$1\frac{1}{2}$$ by $$\frac{3}{2}$$ instead of by 4. Choice B ($$4\frac{1}{2}$$ cups) comes from adding 3 to $$1\frac{1}{2}$$ rather than finding the proper ratio. Choice D ($$4\frac{3}{4}$$ cups) results from miscalculating the scaling factor or making arithmetic errors in the multiplication.

The correct answer is C: 6 cups of nuts.

For ratio problems, always identify what's changing and by what factor, then apply that same factor to the unknown quantity. Converting mixed numbers to improper fractions often makes the arithmetic cleaner and reduces calculation errors.

8

A construction worker pours concrete in three sections: $$3\frac{2}{5}$$ cubic yards in the morning, $$2\frac{3}{10}$$ cubic yards at lunch, and $$1\frac{7}{10}$$ cubic yards in the afternoon. What is the total amount of concrete poured?

$$7\frac{4}{10}$$ cubic yards

$$6\frac{12}{25}$$ cubic yards

$$7\frac{2}{5}$$ cubic yards

$$6\frac{4}{5}$$ cubic yards

Explanation

This problem tests your ability to add mixed numbers with different denominators. When you see mixed numbers being combined, you need to convert to a common denominator before adding.

First, convert all fractions to have the same denominator. The denominators are 5, 10, and 10, so use 10 as the common denominator:

  • $$3\frac{2}{5} = 3\frac{4}{10}$$ (multiply $$\frac{2}{5}$$ by $$\frac{2}{2}$$)
  • $$2\frac{3}{10} = 2\frac{3}{10}$$ (already has denominator 10)
  • $$1\frac{7}{10} = 1\frac{7}{10}$$ (already has denominator 10)

Now add the whole numbers and fractions separately: Whole numbers: $$3 + 2 + 1 = 6$$ Fractions: $$\frac{4}{10} + \frac{3}{10} + \frac{7}{10} = \frac{14}{10} = 1\frac{4}{10}$$

Total: $$6 + 1\frac{4}{10} = 7\frac{4}{10}$$

Convert $$\frac{4}{10}$$ to simplest form: $$\frac{4}{10} = \frac{2}{5}$$, so the answer is $$7\frac{2}{5}$$. This is choice B.

Choice A ($$6\frac{4}{5}$$) adds the whole numbers correctly but makes an error with the fraction addition. Choice C ($$7\frac{4}{10}$$) is correct mathematically but isn't simplified to lowest terms. Choice D ($$6\frac{12}{25}$$) appears to result from incorrect fraction manipulation and wrong whole number addition.

Always convert mixed number answers to simplest form on the ISEE. When denominators differ, find the least common denominator before adding the fractional parts.

9

A recipe calls for $$1\frac{1}{8}$$ cups of milk per serving. How much milk is needed to make $$2\frac{2}{3}$$ servings?

$$3\frac{19}{24}$$ cups

$$2\frac{17}{24}$$ cups

$$3$$ cups

$$2\frac{23}{24}$$ cups

Explanation

This is a multiplication problem involving mixed numbers. When you see "per serving" combined with a number of servings, you need to multiply the amount per serving by the total number of servings.

To solve this, multiply $$1\frac{1}{8}$$ cups per serving by $$2\frac{2}{3}$$ servings. First, convert both mixed numbers to improper fractions: $$1\frac{1}{8} = \frac{9}{8}$$ and $$2\frac{2}{3} = \frac{8}{3}$$.

Now multiply: $$\frac{9}{8} \times \frac{8}{3} = \frac{9 \times 8}{8 \times 3} = \frac{72}{24}$$

Notice that the 8s cancel out, giving you $$\frac{9}{3} = 3$$. So you need exactly 3 cups of milk.

Looking at the wrong answers: Choice A ($$2\frac{17}{24}$$) likely comes from adding the mixed numbers instead of multiplying them - a common mistake when students see fractions and panic. Choice C ($$3\frac{19}{24}$$) might result from calculation errors when working with the improper fractions, possibly from not simplifying $$\frac{72}{24}$$ correctly. Choice D ($$2\frac{23}{24}$$) could come from similar computational mistakes or from incorrectly converting the mixed numbers to improper fractions initially.

The key strategy here is recognizing the word "per" as a multiplication signal. When you see "X amount per unit" and need to find the total for multiple units, always multiply. Also, look for opportunities to cancel common factors early in fraction multiplication - it makes the arithmetic much cleaner.

10

A seamstress has $$8\frac{1}{3}$$ yards of fabric. She uses $$2\frac{3}{4}$$ yards for a dress and $$1\frac{5}{6}$$ yards for a skirt. How much fabric remains?

$$3\frac{3}{4}$$ yards

$$4\frac{7}{12}$$ yards

$$12\frac{11}{12}$$ yards

$$3\frac{1}{4}$$ yards

Explanation

This problem tests your ability to subtract mixed numbers, which requires finding a common denominator and sometimes borrowing when the subtraction becomes challenging.

Start with the original amount and subtract what was used: $$8\frac{1}{3} - 2\frac{3}{4} - 1\frac{5}{6}$$. To work with these fractions, you need a common denominator. The least common multiple of 3, 4, and 6 is 12.

Convert each mixed number: $$8\frac{1}{3} = 8\frac{4}{12}$$, $$2\frac{3}{4} = 2\frac{9}{12}$$, and $$1\frac{5}{6} = 1\frac{10}{12}$$.

Now subtract: $$8\frac{4}{12} - 2\frac{9}{12} - 1\frac{10}{12}$$. Since $$\frac{4}{12}$$ is smaller than $$\frac{9}{12} + \frac{10}{12} = \frac{19}{12}$$, you need to borrow from the whole number. Convert $$8\frac{4}{12}$$ to $$7\frac{16}{12}$$.

Calculate: $$7\frac{16}{12} - 2\frac{9}{12} - 1\frac{10}{12} = (7-2-1) + (\frac{16}{12} - \frac{9}{12} - \frac{10}{12}) = 4 - \frac{3}{12} = 4 - \frac{1}{4} = 3\frac{3}{4}$$.

Choice A) $$3\frac{3}{4}$$ is correct. Choice B) $$4\frac{7}{12}$$ likely results from calculation errors with the common denominator. Choice C) $$3\frac{1}{4}$$ comes from incorrectly handling the borrowing process. Choice D) $$12\frac{11}{12}$$ suggests adding instead of subtracting the fabric used.

When working with mixed number subtraction, always find the common denominator first, then handle borrowing carefully when the fraction part of the minuend is smaller than what you're subtracting.

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