Question 946294
It takes one worker 5 hours to do the same job that it takes another worker 3 hours to do.
 If they work together, in how many hours will the job be done?
:
let t = time required when working together
let the completed job = 1
:
Each will do a fraction of the job, the two fractions add up to 1
{{{t/5}}} + {{{t/3}}} = 1
Multiply the equation by the least common multiple of the denominators, namely: 15,
15*{{{t/5}}} + 15*{{{t/3}}} = 15
 cancel the denominators, then you have: 
3t + 5t = 15
8t = 15
t = 15/8
t = 1.875 hrs