Practice Rational numbers

Rational numbers can be written as a ratio of two integers with a nonzero denominator.

They include fractions and terminating or repeating decimals.

Exercises with solutions

Rational numbers are all numbers that can be written as a fraction of two integers, so they include negative numbers and decimals. For calculating with signs: with the same signs you add the magnitudes, with different signs you subtract the smaller magnitude from the larger and take the sign of the larger.

Exercise 1

Calculate −8 + 3.

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−5

Different signs: 8 − 3 = 5. The larger magnitude belongs to −8, so the result is negative.

Exercise 2

Calculate −8 + (−3).

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−11

Same signs: the magnitudes are added. 8 + 3 = 11 and the result stays negative.

Exercise 3

Calculate −5 · (−4).

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20

Minus times minus gives plus: 5 · 4 = 20.

Exercise 4

Calculate −12 ÷ 4.

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−3

Minus divided by plus gives minus: 12 ÷ 4 = 3, so the result is −3.

Common mistake

Forgetting the sign rule when multiplying and dividing: minus times minus gives plus. And adding the magnitudes even though the signs differ.

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Area: Numbers and arithmeticFrom grade 7 · Grades follow the North Rhine-Westphalia curriculum; other German states may introduce topics at different times.
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