A and B can do a work in 20days, B and C in 25days, C and A in 30days. If A,B and C work together , they will complete the work in?
Choose the most appropriate option:  A) 10 days  B) 12 days  C) 16 days  D) 20 days  E) 25 days

Rationale: "a + b 1 day work = 1 / 20 b + c 1 day work = 1 / 25 c + a 1 day work = 1 / 30 adding we get 2 ( a + b + c ) = 1 / 20 + 1 / 25 + 1 / 30 = 37 / 300 a + b + c 1 day work = 37 / 600 a , b , c can finish the work in 600 / 37 days = 16 days approximately answer is c"
Answer: C