Alex takes 3 hours longer to complete a certain job than Barry does. If they can complete the job

Question

by working together in 3.6 hours, how long would it take Alex to complete the job working
alone?
3.

Answer 1

Immediately assign variables to the time that Alex and Barry take to do the job. Say the time Alex takes is a, and the time that Barry takes is b.

Thus, a = b + 3

You need to add 3 to the time of Barry so that the time of both persons are equal. (eg. if Alex takes 5 hours, Barry would take 2 hours and a = b + 3 would work because 5 = 2 + 3)

If they can complete the job by working together in 3.6 hours, how long would it take Alex to complete the job working alone?
This is where a handy little formula can be used. For things like that (time taken to so something alone and time taken to so the same thing with other people), you can use this:

T is the time they take if they work together. Say there was another person Cyrus also working, and c were the time he usually takes alone to complete the job, then you could still use the formula, but like this:

It's easy, right?

Now, you've got:

and

Simultaneous equations, solve for a

Answer 2

AAAAAAAAAAAHHH it didn't post right

Answer 3

1/b + 1/(b+3) = 1/3.6
or
1/b + 1/(b+3) = 5/18
18(b+3) + 18(b) = 5(b)(b+3)
18b + 54 + 18b = 5b^2 + 15b
5b^2 - 21b - 54 = 0
(5b+9)(b-6) = 0
b = 6
so,
a = 9

1/6 + 1/9 = (3+2)/18 = 5/18