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

[EX Q]: Problem: a reduction of 20 % in the price of oil enables a house wife to obtain 4 kgs more for rs . 600 , what is the reduced price for kg ?
[EX A]: 30

[EX Q]: Problem: the ratio of the radius of two circles is 1 : 3 , and then the ratio of their areas is ?
[EX A]: 1 : 9

[EX Q]: Problem: the ratio of number of boys and girls in a school is 3 : 2 . if there are 100 students in the school , find the number of girls in the school ?
[EX A]:
40