Students from Class 3, Grade 5 went to climb a mountain. The speed of going up the mountain was 4 km/h, and it took 3 hours. They went back down the mountain by the same route, and it took 1 hour less to return. What is their speed of going down the mountain?
五年级三班的同学去爬山，上山的速度是4千米/时，用了3小时；下山按原路返回，返回时少用了1个小时，他们下山的速度是多少？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 * (3/2)</gadget>
<output>6</output>

<result>6</result>