Question 916692
it took john two hours to paint a certain room.
 it took his brother roberts three times slower
how long will it take them if they work together?
:
If John took two hrs and Robert was 3 times slower, Robert would take 6 hrs
:
Let t = time required when working together
let the completed job = 1 (a painted room)
:
Write a shared work equation, each will do a fraction of the job, the two fractions must add up to 1
:
{{{t/2}}} + {{{t/6}}} = 1
multiply the equation by 6, cancel the denominators & you have:
3t + t = 6
4t = 6
t = 6/4
t = 1.5 hrs working together