The task is to generate the correct answer for a given math problem.

Ex Input:
Problem: carl is facing very difficult financial times and can only pay the interest on a $ 10,000 loan he has taken . the bank charges him a quarterly compound rate of 8 % . what is the approximate interest he pays annually ?

Ex Output:
3500

Ex Input:
Problem: by selling an article for $ 225 a person gains $ 75 . what is the gain % ?

Ex Output:
50 %

Ex Input:
Problem: in a group of 160 people , 90 have an age of more 30 years , and the others have an age of less than 20 years . if a person is selected at random from this group , what is the probability the person ' s age is less than 20 ?

Ex Output:
0.44