there are 30 students in a classroom. The ratio of the # of girls to boys was 1:2, how many boys are there?  Choose the correct choice
A) 10  B) 15  C) 20  D) 25  E) 30

Rationale: # of girls = x # of boys = 2 x x + 2 x = 30 3 x = 30 x = 30 / 3 = 10 boys = 2 x = 2 * 10 = 20 answer : c
Answer: C