R can finish a work in 6 days if he works 10 hours a day. S can finish it in 5 days if he works 8 hours a day. If both start a work and work daily for 6 hours, the work will be finished in _____ days.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 4.
According to the given question,
Time taken by R to complete the work = 6 × 10
⇒ 60 hours
Time taken by S to complete the work = 5 × 8
⇒ 40 hours
Let the total work to be done by both R and S LCM(60, 40) be 120 units.
Efficiency of R = 120/60
⇒ 2 units/hour
Efficiency of S = 120/40
⇒ 3 units/hour
Time taken by R and S together to complete the work = 120/5
⇒ 24 hours
If R and S work for 6 hours a day, time taken by them = 24/6
⇒ 4 days