A, B and C can complete a piece of work in 24, 6 and 12 days respectively. Working together, they will complete the same work in:  Choose one.
A) 33 / 7  B) 43 / 7  C) 24 / 7  D) 19 / 7  E) none

Rationale: if a can do a piece of work in n days , then a ' s 1 day ' s work = 1 / n ( a + b + c ) ' s 1 day ' s work = 1 / 24 + 1 / 6 + 1 / 12 = 7 / 24 so , all the three together will complete the job in = 24 / 7 days answer : c
Answer: C