Dad and Xiaoyong went hiking on weekends. The whole journey from the bottom of the mountain to the top of the mountain is 7.2 kilometers. It took them 3 hours to go up the mountain and 1.8 hours to go down the mountain. How many kilometers faster was the speed of going down the mountain than the speed of going up the mountain?
周末爸爸和小勇去登山．从山底到山顶全程有7.2千米，他们上山用了3小时，下山用了1.8小时，下山的速度比上山速度快多少千米？
<gadget id="calculator">7.2 / 1.8</gadget>
<output>4</output>

<gadget id="calculator">7.2 / 3</gadget>
<output>2.4</output>

<gadget id="calculator">4 - 2.4</gadget>
<output>1.6</output>

<result>1.6</result>