Question

You have three-fifths of a pizza leftover, and you plan to eat half of it for lunch. How much of the original pizza do you have left over?

If I have 3/5 of a pizza leftover and I plan to eat 1/2 of it for lunch doesn't that mean you have to divide?

This is the answer they gave me: to find 1/2 of 3/5 of a pizza. When finding a fraction of something, use multiplication (for example, 1/2 of 1/2 = 1/2 x 1/2 = 1/4). Therefore, this is a multiplication problem.

I don't get why I have to multiply instead of dividing when finding a fraction of something? Can someone please explain why? Any help is grateful! Thanks :)

Answer 1

(3/5) / 2 = 3/10

is exactly the same as

(3/5)(1/2) = 3/10

multiplying by 1/2 is dividing by 2
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details:
(3/5) / 2
multiply by 5/5
= 5(3/5)/[5*2]
= 3/10

or
(3/5)(1/2)
multiply by 5/5
3/10