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Chapter 2 · Fractions · page 10 of 68

Multiplying fractions

levelGrade 5
standard5.NF.B.4
practiceFraction operations

Multiply straight across: top times top, bottom times bottom. No common bottom needed. Two thirds of three quarters is six twelfths, which is one half.

How to use it

  1. Multiply the tops.
  2. Multiply the bottoms.
  3. Simplify. Shortcut: cancel a common factor between any top and any bottom before multiplying.

Example

23×34=612=12\frac{2}{3} \times \frac{3}{4} = \frac{6}{12} = \frac{1}{2}
23×34=23×34=24=12\frac{2}{3} \times \frac{3}{4} = \frac{2}{\cancel{3}} \times \frac{\cancel{3}}{4} = \frac{2}{4} = \frac{1}{2}

Where it goes wrong

  • Finding a common bottom first. That is for adding, not multiplying.
  • Cross-multiplying. That is for comparing fractions or solving proportions, not for finding a product.

Related

Dividing fractionsAdding and subtracting fractions
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