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. Work each one on the canvas under it (pen, eraser and clear are in the canvas toolbar; drag the handle below the canvas for more room). Enter your answer in the box (the keypad under it has fractions, exponents, square roots, pi, the degree sign and the symbols < > ≤ ≥ ≠). When a Unit row is shown, tap the unit for your answer. Then press Check. Write fraction answers as improper fractions in lowest terms. Write decimal answers as decimals. The eye at the right of the row shows or hides the worked solution.