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8.05 Multiply fractions by whole numbers

Lesson

Are you ready?

Let's recall how any fraction can be thought of as a multiple of a unit fraction.

We are going to work out how to represent $4\times\frac{1}{3}$4×13 on the number line.

  1. Mark $\frac{1}{3}$13 on the number line.

    01

  2. Now mark $4\times\frac{1}{3}$4×13 on this number line.

    012

Learn

We can extend this to multiply any fraction by a whole number, by thinking of the fraction as a multiple of a unit fraction.

Let's see how we can do this, in the video.

Apply

Question

We are going to work out how to represent $3\times\frac{2}{5}$3×25 on the number line.

  1. First mark $\frac{2}{5}$25 on the number line.

    012

  2. Now mark $3\times\frac{2}{5}$3×25 on this number line.

    012

 

Remember!

We can multiply a fraction by a whole number by thinking of it as a multiple of a unit fraction. For example:

$5\times\frac{3}{8}$5×38 $=$= $5\times3\times\frac{1}{8}$5×3×18
  $=$= $15\times\frac{1}{8}$15×18
  $=$= $\frac{15}{8}$158

Outcomes

5.NF.B.4

Apply and extend previous understandings of multiplication to multiply a fraction or whole number by a fraction.

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