Thirty children from an afterschool club went to the aquarium this is 20% of the children in the club. how many children are in the club

There are 150 children in the after school club. 15 = 10%, 30 = 20%, 45 = 30%, etc. 

150 children, because 30=20%, than 60=40%, 90=60%
120=80%, 150=100% I am making a pattern, and since 20 goes into 100 evenly 5 times, you make 20 into hundred by multiplying by 5, turn 30 into 150 by multiplying THAT by 5.