N:Dure wrote:Richard began driving from home on a trip averaging 30 miles per hour. How many miles per hour must Carla drive on average to catch up to him in exactly 3 hours if she leaves 30 minutes after Richard?
- 35
- 55
- 39
- 40
- 60
At a rate of 30mph, the distance traveled by Richard in 1/2 hour = (30)(1/2) = 15 miles.
For Carla to catch-up 15 miles in 3 hours, the required CATCH-UP rate = 15/3 = 5 miles per hour.
Implication:
To catch up 15 miles in 3 hours, every hour Carla must travel 5 more miles than Richard.
Thus:
Carla's rate = (Richard rate) + 5 = 30+5 = 35 miles per hour.
The correct answer is
A.
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