Gori and Gopal alone can do a piece of work in 9 and 21 days, respectively. In how many days will the work be completed, if they both work on alternate days, starting with Gopal?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 13.
Total work = LCM of 9 and 21 = 63
Efficiency of Gori = 63/9 = 7
Efficiency of Gopal = 63/21 = 3
Work done in 2 days (Starting with Gopal) = 3 + 7 = 10
Work done in 12 days = 12(10/2) = 60
Remaining work = 63 - 60 = 3
On the 13th day, Gopal did the remaining work.
Total time required = 13 days