Math

While driving on the highway, Dave averages 60 miles per hour. In the city, he averages 30 miles per hour. On a trip to his grandmother's house, Dave drives 2 3/5 hours on the highway and 1 1/5 hours in the city.

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  1. The question: What is Dave's average speed for the entire trip to his grandmother's house? Round to the nearest tenth.

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  2. average speed = totaldistance/totaltime
    since for each leg of the trip, distance = speed * time, we have

    avgspeed = ((2 3/5 * 60)+(1 1/5 * 30))/(2 3/5 + 1 1/5)
    = (156+36)/(3 4/5) = ?

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  3. So I got 50.52631..... and I rounded that to 50.5. Is this correct?

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