Add and Subtract Rational Numbers, On Level Answer Key

Grade 7 rational numbers: adding and subtracting positive and negative fractions, mixed numbers, and decimals. Monday practice at grade level.

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Lesson Notes

Use the same three moves every time: rewrite (common denominator or aligned decimals), combine (add or subtract), simplify (lowest terms).

Worked example

$-\tfrac{5}{6} - \tfrac{1}{4}$: subtracting is adding the opposite, and the common denominator is 12.

$-\tfrac{10}{12} - \tfrac{3}{12} = -\tfrac{13}{12}$

Mixed numbers: change to improper fractions when a negative is involved, so the sign applies to the whole number.
Decimals: line up the decimal points and pad with zeros.
Three or more terms: work left to right, one operation per line.

Watch the sign. $-3.5 + 1.25$ is a subtraction of sizes ($3.5 - 1.25$) with the sign of the larger size, negative.

25 problems. Show your work in the space under each problem, then put a box around your answer. Write fraction answers as improper fractions in lowest terms. Write decimal answers as decimals. On screen, the eye at the right of each problem shows or hides the worked solution.