Question

If A and B can do a piece of work in 20hrs. B and C can do it in 15 hrs and C and A can do it
in 12 hrs. In how many hours will they finish the work together and separately​

Answer 1

Step-by-step explanation:

Time taken by A, B and C working together to finish a work = 8 hours 

Work done by A, B and C working together in one hour = 1/8

Time taken by A alone to finish the work = 20 hours

Work done by A in 1 hour = 1/20 

Time taken by B alone to finish the work = 24 hours

Work done by B in 1 hour = 1/24

So, work done by C  = 1/8 - (1/20 + 1/24)

Taking LCM of the denominators and then solving it.

⇒ [15 - (6 + 5)]/120

⇒ (15 - 11)/120

⇒ 4/120

⇒ 1/30 

So, C alone can do the same work in 30 hours