Question

6. A can do a piece of work in 24 hours while B alone can do it in 16 hours. If A. B and C
working together can finish it in 8 hours, in how many hours can C alone finish the work?
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Answer 1

Answer:

When A does the work in 6 hours and B does it in 16 hours, why should A, B and C, three of them together take 8 hours to finish the work. It should be less than 6 hours!

A does 1/6th of the work in an hour, while B does 1/16th of the work in an hour. A, B and C do 1/8th of the work in an hour.

So C does (1/8) - (1/6) - (1/16) = (6/48) - (8/48) - (3/48) = (6–8–3)/48 = -11/48th part of the work in an hour. So he will complete the work in -48/11 = -4 and 4/11 th hour.

A negative answer for C as (-4 and 4/11th hour) is impossible. It means C is a hindrance to the work and he is obstructing A and B from doing their work!