Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Problem: two trains of equal are running on parallel lines in the same direction at 45 km / hr and 36 km / hr. the faster train passes the slower train in 36 sec. the length of each train is ?
Options: a. 45, b. 88, c. 66, d. 55, e. 22
a

Problem: what is the smallest number by which 2880 must be divided in order to make it into a perfect square ?
Options: a. 3, b. 4, c. 5, d. 6, e. 7
c

Problem: if 2 a = 3 b and ab ≠ 0, what is the ratio of a / 3 to b / 2 ?
Options: a. 27 / 8, b. 8 / 27, c. 1, d. 9 / 4, e. 81 / 64

c