Question

P alone can finish a piece of work ‘M’ in 8 days while Q takes 4 days to finish it alone. P, Q and R working together can finish the work ‘N’ which is 7 times of work ‘M’ in 8 days. How long will R take to finish work ‘N’, when working alone?

A 16 days Correct Answer Incorrect Answer
B 15 days Correct Answer Incorrect Answer
C 13.5 days Correct Answer Incorrect Answer
D 12 days Correct Answer Incorrect Answer
E 14 days Correct Answer Incorrect Answer

Solution

 Let the work ‘M’ = 8 units (LCM of 8 and 4) Efficiency of P = 8/8 = 1 units Efficiency of Q = 8/4 = 2 units Efficiency of P, Q and R = (8 × 7)/8 = 7 units per day Efficiency of R = 7 – (1 + 2) = 4 units per day Time taken by R to finish work ‘N’ = 56/4 = 14 days

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