A man drives 60 mph for 3 hours. How fast would he have to drive over the next 2 hours to get an average speed of 70 mph? Let's answer step by step:
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To have an average speed of 70 mph over 5 hours he needs to travel 70 * 5 = 350 miles. He drove 60 * 3 = 180 miles in the first 3 hours. He needs to travel another 350 - 180 = 170 miles over the next 2 hours. His speed needs to be 170 / 2 = 85 mph. The answer: 85.
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