Skip to content
Exit presentation

Working with Fractions

How many of these fit inside that

A tailor has 3/4 of a ribbon roll. Each trim, a short piece of ribbon, takes 1/8 of a roll. How many trims fit?

A strip cut into eighths.
Step 1 of 4
  1. A strip cut into eighths.
  2. 3/4 of the roll is 6/8.
  3. Number the 6 eighth-sized trims.
  4. 3/4 ÷ 1/8 = 6.

Dividing counts copies

6 trims fit. Each trim is one copy of 1/8.

Start with a small case. How many quarters fit inside a half? Two of them. So 1/2 ÷ 1/4 = 2.

Dividing by a fraction is the same as multiplying by its reciprocal.

3/4 ÷ 1/8 is 3/4 × 8/1. Tops: 3 × 8 = 24. Bottoms: 4 × 1 = 4. 24/4 is 6.

The number of copies is not always whole. 2/3 ÷ 1/4 is 2/3 × 4/1, which is 8/3. And 8 ÷ 3 is 2 with 2 left, so 2 2/3.

Slide to lay copies along the strip in the lab. Count how many fit.

Loading lab…

Jump to lesson

This track

  1. 0 Start here
  2. 1 More than one whole
  3. 2 Renaming until the pieces match
  4. 3 Adding pieces that do not match
  5. 4 Taking one fraction from another
  6. 5 Wholes and parts together
  7. 6 Checkpoint: renaming, adding and taking away
  8. 7 A fraction of a whole number
  9. 8 A fraction of a fraction
  10. 9 When multiplying makes it smaller
  11. 10 The number that undoes a fraction
  12. 11 How many of these fit inside that
  13. 12 Checkpoint: multiplying and dividing
  14. 13 Cancel before you multiply
  15. 14 Share a fraction equally
  16. 15 When dividing makes it bigger
  17. 16 A fraction of what is left
  18. 17 The big picture
  19. 18 Track quiz

Other tracks