Master Wang drove to buy chemical fertilizers at a speed of 60 km/h, arrived in 4 hours, and returned in 6 hours. What is the speed of return?
王师傅开车去买化肥，去时的速度是60千米/时，4小时到达，返回用了6小时．返回的速度是多少？
<gadget id="calculator">4 / 6</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">60 * (2/3)</gadget>
<output>40</output>

<result>40</result>