P, Q and R can complete a task in 20, 30, and 60 days, respectively. How many days will it take to finish the work if P is helped by Q and R every third day?
Show answer & explanation
Correct answer: D
Explanation
The Correct answer is option 4 i.e. 15
Given that
P, Q, and R can complete a task in 20, 30, and 60 days, respectively.
Total work = LCM (20 , 30 , 60) = 60
The efficiency of P = 60/20 = 3
The efficiency of Q = 60/30 = 2
The efficiency of R = 60/60 = 1
if P is helped by Q and R every third day
the work is completed in 3 days = P + P + (P + Q + R) = 3 + 3 + (3 + 2 + 1) = 12
Hence, the total work is completed in = (60 × 3)/12 = 15 days