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A car travels at 100 km/hr for 2.0 hr, at 60 km/h for the next 2.0 h, and finally at 80...

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gretjxfj | Student, Undergraduate | eNoter

Posted February 24, 2012 at 7:22 PM via web

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A car travels at 100 km/hr for 2.0 hr, at 60 km/h for the next 2.0 h, and finally at 80 km/h for 1.0 h. find its average speed for the entire 5.0 h.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted February 24, 2012 at 8:55 PM (Answer #1)

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The car travels at 100 km/hr for 2.0 hr, at 60 km/h for the next 2.0 h, and finally at 80 km/h for 1.0 h. The average speed of the car over the entire 5 hours has to be determined. This is equal to the total distance traveled in 5 hours divided by 5.

The distance traveled by the car in the first 2 hours is 200 km, it travels 120 km in the next 2 hours and 80 km in the last hour. Adding the distances traveled gives a total of 200 + 120 + 80 = 400 km.

The average speed of the car over the entire 5 hour period is 400/5 = 80 km/h.

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