8. Multiply and divide fractions
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.
Mark $\frac{1}{3}$13 on the number line.
Now mark $4\times\frac{1}{3}$4×13 on this number line.
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.
First mark $\frac{2}{5}$25 on the number line.
Now mark $3\times\frac{2}{5}$3×25 on this number line.
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 |