Idea 6of 22Builds onMultiplying is adding the same piece again
The whole number becomes the numerator
What is 7 × 1/5, without drawing it?
Today you'll discover
- a quick way to multiply by a unit fraction
- why the bottom number stays the same
- two mix-ups to avoid
Think firstSeven pieces, each one fifth
What is 7 × 1/5?
Decide first, then press Next. Watch the top number; the bottom one never moves.
Seven tinted pieces, each 1/5, slide together into bars one whole wide and are counted 1/5 up to 7/5. Five fill the first bar; two sit in a dashed second bar. The sentence 7 × 1/5 = 7/5 = 1 2/5 appears underneath. The last step shows 6 × 1/8.
See the whole ideathe big idea and the key word, in one place
The big idea
To multiply by a unit fraction, the whole number becomes the numerator: 7 × 1/5 = 7/5.
Easy to get wrongDo not multiply the bottom number. 7 × 1/5 is not 7/35: you took more fifths, you did not cut them smaller.
Any unit fraction2 × 1/3 = 2/3, 5 × 1/4 = 5/4, 6 × 1/8 = 6/8. The whole number always lands on top.
Key word
- product
- the answer to a multiplication; the product of 7 and 1/5 is 7/5
Ready to use it?
- Multiply a whole number by a unit fraction.