Multiple choice

P and Q can do a piece of work in 40 days. Q and R can do it in 120 days. Q alone could finish it in 180 days. In how many days will P and R working together finish the work?

  1. 35

  2. 50

  3. 25

  4. 45
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let total work = LCM of 40,120,180 = 360 units. P+Q = 360/40 = 9 units/day. Q+R = 360/120 = 3 units/day. Q = 360/180 = 2 units/day. So P = 9-2 = 7 units/day, R = 3-2 = 1 unit/day. P+R = 8 units/day, taking 360/8 = 45 days. Answer D is correct.

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