Why does it take 4 copies of 1 tenth to equal 2 copies of 1 fifth when the whole is the same?

Answer 1

Well, honey, it's simple math. A tenth is smaller than a fifth, so you need more tenths to make up the same amount as a fifth. It's like trying to fit four tiny puzzle pieces into the same space as two slightly bigger ones - you do the math, you get the answer.

Answer 2

One tenth is half the size of one fifth. It makes sense it would take twice as many of them to reach the same value.