Q) P can complete a work in 12 days working 8 hours a day. Q can complete the same work in 8 days working 10 hours a day. If both P and Q work together, working 8 hours a day, in how many days can they complete the work?

a) 5 5/11 days                     b) 5 6/11 days               

c) 6 5/11 days                     d) 6/11 days

Ans:

P finish the work in 12 x 8 = 96 hrs

∴ P’s 1 hr work = 1/96

Q finish the work in 8 x 10 = 80 hrs

∴ Q’s 1 hr work = 1/80

∴ (P + Q)’s 1 hr work = 1/96 + 1/80 = 11/480

Since (P + Q) do 11/480 work is done in = 1 hr

∴ (P + Q) do full work in = 1/(11/480) = 480//11

At 8 hrs a day, days taken = (480/11) /8 = 60/11 days = 5 5/11 days

Hence, Answer is [A].

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