SOLUTION: If you drive 71 mph the first hour and 85 mph the second hour, How many mph do you need to drive to reach 200 mile destination?

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Question 873255: If you drive 71 mph the first hour and 85 mph the second hour, How many mph do you need to drive to reach 200 mile destination?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
The trip as was done:
71%2A1%2B85%2A1=200 but you already know this was a 1+1=2 hour trip for 200 miles.
71%2B85=200
156%3C%3E200

Let r = the constant speed desired, instead of the mixed rates.
r%2A2=200
r=100

The question is not well formed. The two hour trip as done is 29 miles short of the whole 200 mile trip.