Firstly here's the Excel file: Fraction Multiplication (simple)
"Save Target As", and select where you want the file to be saved.
There's another version of this file called Fraction
which shows more of the stages in the
justification. However, I prefer the simpler version, it feels less
Question: What's 2/5 of . . . 1/3, 2/3, 3/4, 3/5, or 4/5?
Here's what I say and do if I'm using Fraction Multiplication
(extra); with the simple version, what I say will be much the
- Set the spinners to get 2/5 of 1/3
- Show 1/3 at the top of the board or screen
- Next look at 1/5 of 1/3 and observe that this is the same as
- Show 2/5 of 1/3 - obviously 2/15
- Change the spinner to get 2/5 of 2/3, and discuss how this
answer can be worked out almost instantly from the first one.
- 2/5 of 2/3 would be . . . 2/15 from the first third, then
another 2/15 from the second . . . in other words: 4/15
- Move on to think about 2/5 of 3/4
- Using fifths of quarters means we will be counting up
- 1/5 of 1/4 is 1/20
- 1/5 of each of the three quarters (1/5 of 3/4 ) is 1/20 three
- So another 1/5 (that's two fifths of 3/4 in all) makes another
3/20 , or 6/20 in all. * Sometimes, as in this case, the result can
be expressed more simply: 3/10 instead of 6/20