SOLUTION: Hi donald can complete a job in 20minutes.if he has been working on the job for 10 min, then he is joined by sam and the job is finished in another 6 min. How long would it have t

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Question 1052301: Hi
donald can complete a job in 20minutes.if he has been working on the job for 10 min, then he is joined by sam and the job is finished in another 6 min. How long would it have taken sam to do the job by himself.
thanks
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
donald can complete a job in 20minutes.
if he has been working on the job for 10 min, then he is joined by sam and the job is finished in another 6 min.
How long would it have taken sam to do the job by himself.
:
let s = time required by Sam by himself
Donald worked 10+6 = 16 min
let the completed job = 1
each does a fraction of the job, the two fractions add up to 1
:
+ = 1
multiply equation by 20s, cancel the denominators:
16s + 6(20) = 20s
120 = 20s - 16s
120 = 4s
s = 120/4
s = 30 min for Sam to do the job by himself.
:
:
See if that checks out
+ =
+ = 1