Question

An earthquake strikes and an isolated area is without food or water. three crews arrive. one can dispense needed supplies in 4545 ​hours, a second in 9090 ​hours, and a third in 6060 hours. how long will it take all three crews working together to dispense food and​ water?

Answer 1

If we say 1515 is one part, A is doing 3, B is doing 6, C is doing 4. We have 13 parts in total, so we divide them proportionally:

Xb+2xa+1.6xc=13

A= 5.65 parts

B= 2.82 parts

C= 4.52 parts

B would take 9090 to do 13

But will do T To do 2.82

T= 1,971.8 hours

Hope you get it!