SOLUTION: John and Fred must mow the lawn before they can go swimming. By themselves, John would take 30 minutes and Fred would take 45 minutes. How long would it take to mow the lawn with b

Question 55990: John and Fred must mow the lawn before they can go swimming. By themselves, John would take 30 minutes and Fred would take 45 minutes. How long would it take to mow the lawn with both working together?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
John and Fred must mow the lawn before they can go swimming.
:
By themselves, John would take 30 minutes and Fred would take 45 minutes. How long would it take to mow the lawn with both working together?
:
Let t = time in minutes working together
:
During this time we can say John would do t/30 of the job and
Fred would do t/45 of the job
:
Let the completed job = 1, giving us an easy equation:
:
+ = 1
:
We can get rid of the denominators by mult by 90, then we have:
3t + 2t = 90
:
5t = 90
:
t = 90/5
:
t = 18 min when they work together
:
:
Check our solution: + = + = 1

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