If A is thrice as fast as B and together can do a work in 24 days. In how many days A alone can do the work?  Choose the most appropriate option.
A) 36 B) 42 C) 28 D) 32 E) 45

Rationale: "a ’ s one day ’ s work = 1 / x b ’ s one day ’ s work = 1 / 3 x a + b ’ s one day ’ s work = 1 / x + 1 / 3 x = 1 / 24 = 3 + 1 / 3 x = 4 / 3 x = 1 / 24 x = 24 * 4 / 3 = 32 answer : d"
Answer: D