Rakshit, Ajay, and Satish are sanitation workers in a Municipal Corporation. Rakshit alone takes 20 hours to clean a drain while Ajay takes 12 hours when working alone to do the same. All three together take only 5 hours to clean the drain. In how many hours, can Satish complete the work alone?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 15.
Rakshit alone can clean a drain = 20 hours
Ajay alone can clean a drain = 12 hours
Rakshit, Ajay, and Satish can clean a drain = 5 hours
Total work = efficiency of 20, 12, and 5 = 60 unit
Efficiency = Total work/Total hours
Efficiency of Rakshit = 60/20 = 3 unit per hour
Efficiency of Ajay = 60/12 = 5 unit per hour
Efficiency of Rakshit, Ajay, and Satish = 60/5 = 12 unit per hour
So, the efficiency of Satish = 12 - (5 + 3) = 4 unit per hour
So, Satish alone can clean a drain = 60/4 = 15 hours