A can do a work in 15 days and B in 20 days. If they work on it together then in how many days required to complete the work?	Choose the correct option
A) 300 / 31 B) 300 / 35 C) 300 / 21 D) 300 / 15 E) 300 / 20

Rationale: person ( a ) ( b ) ( a + b ) time - ( 15 ) ( 20 ) ( 300 / 35 ) rate - ( 20 ) ( 15 ) ( 35 ) work - ( 300 ) ( 300 ) ( 300 ) therefore a + b requires ( 300 / 35 ) days to complete entire work = 300 / 35 answer is b
Answer: B