P and Q together can complete a work in 20 days. If P alone can complete the same work in 36 days, then in how many days Q alone can complete the same work?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 45 days
Let the total work be LCM of 20 and 36 i.e 180 unit.
Efficiency = Total work/Total time taken
Efficiency of (P + Q) = 180/20 = 9.
Efficiency of P = 180/36 = 5.
Efficiency of Q = (Efficiency of P + Q) - Efficiency of P.
Efficiency of Q = 9 - 5 = 4.
Time taken to complete the work by Q alone = 180/4 = 45 days.