Aman and Rajan are working at a construction site. In an engineering experiment, Aman is constructing a wall, while Rajan is demolishing that wall. Aman can completely build the wall in 15 days, while Rajan will take 20 days to completely demolish the wall. In how many days will the complete wall be built for the first time if they work on alternate days, with Aman working on the 1st day?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 113.
Total work = LCM of 15 and 20 = 60
Constructing rate of Aman = 60/15 = 4
Demolishing rate of Rajan = 60/20 = 3
Total work of Aman and Rajan in 2 days = 4 - 3 = 1
In 112 days, they will complete = 1 × (112/2) = 56
At the 113th day, Aman will be the 4 unit of remaining work.
Hence, the complete wall will be built for the first time in 113 days.