SOLUTION: One roofing crew can finish a 2,800-square-foot roof in 12 hours, and another crew can do the job in 10 hours. If they work together, can they finish before a predict rain in 5 hou

Question 866734: One roofing crew can finish a 2,800-square-foot roof in 12 hours, and another crew can do the job in 10 hours. If they work together, can they finish before a predict rain in 5 hours?
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
The rates of each crew are:
and JOBS per HOUR.

The way uniform rates situations go, . In the kind of application for your example, x is time in hours and y is how much or many jobs. The unit of R is jobs per hour and R is a rate. The rate of each crew working together is the sum of their individual rates, so:

jobs per hour.

Now, if rain will come in 5 hours, will this 5 hours be enough time to do ONE complete job?
? Is this true or false?

FALSE.
The two crews together will not be able to finish the roof before the rain prediction time.
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