SOLUTION: There are 630 dishes that need to be rinsed. John can rinse them in 70 min by himself it will take his friend Bob 105 min to rinse these dishes. How long will it take them if they

Question 541710: There are 630 dishes that need to be rinsed. John can rinse them in 70 min by himself it will take his friend Bob 105 min to rinse these dishes. How long will it take them if they rinse these 630 dishes together?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
There are 630 dishes that need to be rinsed.
John can rinse them in 70 min by himself it will take his friend Bob 105 min to rinse these dishes.
How long will it take them if they rinse these 630 dishes together?
:
Do it as a "shared work" equation
:
Let t = time required when they work together
Let the completed job = 1 (the rinsing of 630 dishes)
:
Each will do a fraction of the job, the two fractions add up to 1
:
+ = 1
multiply by the LCM of 70 & 105 which is 210
210* + 210* = 210
Cancel the denominators and you hav
3t + 2t = 210
5t = 210
t = 42 min together
:
:
Check this
+ = 1
.6 + .4 = 1

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