IXL | Add and subtract rational numbers: word problems

Kelly bought two rolls of tape. The first roll had 4.5 meters of tape and the second roll had 6.3 meters of tape. How many meters of tape did Kelly buy in all?

meters

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Learn with an example

question

Brennan made cookies. He used 4/5 of a cup of flour and 1/3 of a cup of sugar. How much more flour than sugar did Brennan use?

Write your answer as a fraction or as a whole or mixed number.

cups

solution

Find how much more flour was used by subtracting 1/3 from 4/5.

To subtract the fractions, you can use the least common denominator. The least common denominator is the smallest whole number that is a multiple of both 5 and 3.

5 and 3 are prime numbers. You do not need to factor them. Multiply the prime numbers:

3 × 5 = 15

The least common denominator is 15. Find equivalent fractions with 15 as the denominator.

4 × 3

5 × 3

1 × 5

3 × 5

Now subtract the fractions. Subtract the numerators and keep the denominators the same.

−

Brennan used 7/15 of a cup more flour than sugar.

Looking for more? Try these:

Lesson: Adding and subtracting rational numbers

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Not feeling ready yet? These can help:

B.6Add and subtract rational numbers

D.2Add and subtract decimals: word problems

G.4Add and subtract mixed numbers: word problems

Lesson: Adding and subtracting rational numbers

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