Question 545003
Tom and Jack are shingling a roof.
Tom takes 75% of the time Jack does to shingle a roof.
 Together they finish the roof in 5 hours.
A monkey comes along and pulls the shingles off in 9 hours.
 How long does it take Tom, Jack and the monkey to shingle one roof?
:
let t = time required when all three are on the job
let the completed job = 1 (a shingled root)
we can replace Tom & jack with 5 hrs, a simple shared work equation then:
:
{{{t/5}}} - {{{t/9}}} = 1
multiply by 45 and we have
9t - 5t = 45
4t = 45
t = {{{45/5}}}
t = 11.25 hrs. 11 hrs 15 min