X and Y can do a piece of work in 20 days and 12 days respectively. X…

Question

X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?

Accepted Answer

Option B. 10 days. Answer & Solution Answer: Option B Solution: & work\, done\, by\, X\, in\, 4\, days & = 120 × 4 = 1/5 & Remaining\, work & = 1 - 1/5 = 4/5 & ( X + Y ) 's\, 1\, day's\, work & = 120 + 112 = 860 = 215 & Now, 215 work\, is\, done\, by\, X\, and\, Y\, in\, 1\, day. & So,\,4/5\, work…