P and Q can do a piece of work in 14 days. Q and R together can do it in 21 days. If P is twice as good a workman as R, then in how many days Q alone can do the work?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 42 days
According to the question
(P + Q) × 14 = (Q + R) × 21
(P + Q)/(Q + R) = 3/2
Given that
P = 2R
Now, (2R + Q) × 2 = (Q + R) × 3
R = Q
Hence, The efficiency of P, Q, and R = 2, 1, and 1
Q can alone do the work = 42/1 = 42 days