A does 4/5th of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
Choose the most appropriate option
A) 23 days  B) 37 days  C) 37 ½ days  D) 40 days  E) 41 days

Rationale: explanation : a can finish the whole work in 20 × 5 / 4 days = 25 days a and b together finish the whole work in 5 × 3 days = 15 days therefore , b can finish the whole work in 25 b / 25 + b = 15 25 b = 15 ( 25 + b ) = 375 + 15 b 10 b = 375 and b = 375 / 10 = 37 ½ days . answer : option c
Answer: C