In a certain school, the ratio of boys to girls is 5 to 13. If there are 160 more girls than boys, how many boys are there?  Answers: A) 100 B) 36 C) 45 D) 72 E) 117

Rationale: "the ratio of b to g is 5 : 13 and the other data point is g are more than boys by 160 . . . looking at the ratio we can say that the 8 ( 13 - 5 ) extra parts caused this diff of 160 . so 1 part corresponds to 160 / 8 = 20 and so 5 parts correspond to 5 * 10 = 100 . a"
Answer: A