Presentation on theme: "Fractions: Multiplying by more interesting fractions – and then DIVIDING by them. (Part Two)"— Presentation transcript:
Fractions: Multiplying by more interesting fractions – and then DIVIDING by them. (Part Two)
To find 1/8 of something, we divide that thing by 8. What if we wanted to know what 3/8 of something was?
You’d be doing the same thing 3 times, so you would multiply by 3.
(72 is a whole number – so it’s all in one group. 72 ÷1 is… 72.) “John has saved 5/6 of the 72 dollars he needs. How much has he saved? How much does he still need to save?” … Of means multiply, so this problem will look like this:
If I divide that 72 dollars into 6 groups (as the denominator tells me to do), then each “1/6” will have 12 dollars. 6/6 of 72 will be 6 out of six… the whole thing. 6/6 is 1… 1 x 72 is 72.
5/6 is going to be most of the money… 5 x 12 or 60 dollars. 5/6 is going to be most of the money… 5 x 12 or 60 dollars.
Of means multiply… BUT if you multiply by a fraction that’s smaller than one, you don’t have your “whole thing” – so your answer will be smaller. So… 5/6 of 72 is the same as 1/6 of 72…which is 12… times 5, which is 60.
It would be the same as ½. How much would 3/6 of 72 be?
We could draw every fraction to check that out… or we could practice division… but if the numerator is half of the denominator, then the fraction is equivalent to ½.
Which of these fractions are the same as a half?
How could you tell which ones were *more* than a half?
Dividing by fractions But enough with the multiplying, already… time to cover a division problem that is much easier to understand when you can see it.
WATCH YOUR LANGUAGE!!!!!!! Divided by doesn’t mean divided into… doesn’t me a fraction of. If I say 6 ÷ 6, my answer will be the number of times I can get six away from six, which is ONE WHOLE TIME. As a fraction, that would look like this: