student is climbing a mountain, and it takes 4 hours to go up and down the mountain. If he takes 2.4 hours to go up the mountain and returns the same way, and the speed of going down the mountain is 1.5 kilometers per hour, how many kilometers per hour is his uphill speed?
一个学生在爬山中，上山下山共用4小时，如果他上山用2.4小时，原路返回，下山速度是每小时1.5千米，则他的上山速度是每小时多少千米？
<gadget id="calculator">4 - 2.4</gadget>
<output>1.6</output>

<gadget id="calculator">1.6 / 2.4</gadget>
<output>0.666667</output>

<gadget id="calculator">1.5 * 0.666667</gadget>
<output>1.000001</output>

<result>1.000001</result>