Time required varies directly with the number of jobs
and inversely with the number of workers.
I found this problem from long ago, which is worded for combined variation,
to show the other tutors that combined variation is probably what we are
supposed to use on these type problems. Notice how the problem is worded.
The number of hours h that it takes m men to assemble x machines varies directly
as the number of machines and inversely as the number of men.
It really isn't necessary for the problem to tell us that because its easy for
any student to see from plain common sense. In other words:
1. It's easy to see that if the number of men is held constant, the more
machines there are, the more hours will be required, Also, the fewer machines,
the fewer hours will be required. That is DIRECT variation.
and
2. It's easy to see that if the number of machines is held constant, the more
men there are, the fewer hours will be required. And the fewer men there are,
the more the hours that will be required. That is INVERSE variation.
If four men can assemble 12 machines in four hours,
how many men are needed to assemble 36 machines in eight hours?
Multiply by 3m
It will require 6 men.
Edwin
