In the military training of college students, they will walk 15 kilometers in 4 hours on the first day, and 5 hours in the second day, 6 kilometers per hour. How many kilometers per hour on average for two days?
大学生军训，第一天4小时行15千米，第二天行5小时，每小时行6千米．两天中平均每小时行多少千米．
<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<gadget id="calculator">15 + 30</gadget>
<output>45</output>

<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">45 / 9</gadget>
<output>5</output>

<result>5</result>