SOLUTION: It takes you 32 minutes to build a sand castle by yourself and it takes your sister 37 minutes to build a sand castle by herself. How many minutes does it take the two of you to bu

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Question 792375: It takes you 32 minutes to build a sand castle by yourself and it takes your sister 37 minutes to build a sand castle by herself. How many minutes does it take the two of you to build 9 sand castles? Round answer to nearest tenth.
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
Uniform Rates, Task-Completion Problem.
The task is "build a sand castle". The rate would be in units of tasks per minute.

You, 1/32 castles per minute
Sister, 1/37 castles per minute
The rate of You + Sister working together is simply the sum of those two rates.

Let the unknown time in minutes to build 9 castles be m.
highlight%28%281%2F32%2B1%2F37%29%2Am=9%29
Solve for m. A useful guideline is to hold all the computations until AFTER you solve for m; and then finish by performing the computations.

32%2A37%281%2F32%2B1%2F37%29m=9%2A32%2A37
%2837%2B32%29m=9%2A32%2A37
highlight%28m=%289%2A32%2A37%29%2F%2837%2B32%29%29---------this is now where you would want to finish with the computations.