20% as a fraction is 1/5
25% is 1/4
40% is 2/5
and 70% is 7/10
Depending on what your fraction is, you can find the answer in the fraction itself-
20%, you can take 20, 5 times to get to 100. Hence 1/5.
25 can go into 100 4 times (1/4)
40 is just 20 twice, so its 2/5.
Take 10 7 times and get 7/10.
Hope this helps a bit :)