Alice and Bob can complete a job in 2 hours.
Alice and Charlie can complete the same job in 3 hours.
Bob and Charlie can complete the same job in 4 hours.
How long will the job take if Alice, Bob, and Charlie work together?

This question requires some tricky logic and math work. Ultimately, you need to set up a series of equations such as 2(A+B) = 1 for the first statement, 3(A+C) = 1 for the second statement, and 4(B+C) = 1 for the third statement. Then, you need to combine all of those into the equation t(A+B+C) = 1 and solve for t. By multiplying the previous statements by their lowest common multiple, we can deduce that t = 24/13, or approximately 1 hour and 51 minutes. Phew! That was a tricky one, but good work.

Asked by Ben Jenkins · Last updated 3 years ago · 1.1K views · SOURCE