P, Q, and R can complete a piece of work in 10 days, 15 days, and 20 days, respectively. If they work together, in how many days can they finish the same work?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 4.
P, Q, and R can complete a piece of work in 10 days, 15 days, and 20 days
L.C.M (10, 15, and 20) = 60
The efficiency of P = 60/10 = 6 units
The efficiency of Q = 60/15 = 4 units
The efficiency of R = 60/20 = 3 units
Time taken by all three to complete the work = 60/(6 + 4 + 3)
⇒ 60/13 = 4