Question

If it rained 3 days out of 20 days what would the percentage be

Answer 1

How many 20 going into 100

Five 20's 
so 5 x 20 = 100 
We got our 100%
Now since we multiplied 20 by five we will do the same with 3.
3 x 5 = 15
now you get 15/100

15%
It rained 15% of the time