Question 184823
A welder requires 25 hrs to do a job on his own. After a welder and apprentice
 work on job together for 10 hours, the welder goes to another job.
 The apprentice finishes the job in 17 more hours. 
How long would it take the apprentice to do the whole job alone
:
Let t = time required by the job by himself
:
Let the completed job = 1
:
appren works a total 27 hrs
:
Welder's portion + appren portion = completed job
{{{10/25}}} + {{{27/t}}} = 1
multiply equation by 25t to get rid of the denominators, results:
10t + 25(27) = 25t
675 = 25t - 10t
15t = 675
t = {{{675/15}}}
t = 45 hrs hrs; the appren working alone
;
;
Check solution
{{{10/25}}} + {{{27/45}}}
.4 + .6 = 1