A and B can do a piece of work in 10 days, B and C in 5 days, C and A in 15 days. How long will C take to do it?  Choose the correct option: A) 77 days B) 55 days C) 12 days D) 33 days E) 11 days

Rationale: 2 c = 1 / 5 + 1 / 15 – 1 / 10 = 1 / 6 c = 1 / 12 = > 12 days answer : c
Answer: C