Module 4 · Fractions · Lesson 16 of 39

Multiplying and dividing fractions

Multiply straight across; to divide, multiply by the reciprocal.

In this lesson · about 12 minutes

  • Multiply fractions
  • Divide fractions by multiplying by the reciprocal
  • Multiply a fraction by a whole number

Multiply: numerators times numerators, denominators times denominators. 34 × 17 = 3 × 14 × 7 = 328. No common denominator needed.

Divide: flip the second fraction (its reciprocal) and multiply. 34 ÷ 17 = 34 × 71 = 214. A fraction whose top is bigger than its bottom, like 214, is called improper, and that's fine.

Whole numbers: write the whole number over 1 first. 34 × 7 = 34 × 71 = 214.

Worked example

Divide 2/3 ÷ 4/11

Turn the division into multiplication by the reciprocal.

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