Question 781615
Stefan can clean an attic in 16 hours.
 Ryan can clean the same attic in 10 hours.
 Find how long it would take them if they worked together?
:
Here is an easy way to do these "shared work" problems
:
let t = time required to complete the job when they work together
: 
let the completed job = 1, (a cleaned attic)
Each will do a fraction of the job, the two fractions add up to 1
:
{{{t/16}}} + {{{t/10}}} = 1
multiply by the least common multiple of 16 and 10, that's 80
80*{{{t/16}}} + 80*{{{t/10}}} = 80*1
cancel the denominators and you have
5t + 8t = 80
13t = 80
t = 80/13
t = 6.154 hrs working together
:
:
Check this on your calc
6.154/16 + 6.154/10
.385 + .615 = 1; confirms our solution of t = 6.154 hrs