A. Group of cross country runners decided to go on an hour and a half run. During the first hour, they ran a total of 13 kilometers. Then, they ran 5.0 kilometers during the next half an hour. What was the group's average speed for the entire run?

The average speed for the entire run is 12 km/h.

Explanation:      

The average speed is given by the following equation:

Where:

: is the total distance

: is the total time

If during the first hour, they ran a total of 13 kilometers and then, they ran 5.0 kilometers during the next half an hour we have:

Hence, the average speed is:

Therefore, the average speed for the entire run is 12 km/h.

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explanation:

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it is called kinetic energy