Uncle Wang sent a cart of vegetables to the vegetable market at a speed of 40 km/h. It took 5 hours to deliver it, and it only took 4 hours to return. What was the speed when returning?
王叔叔把一车蔬菜送到菜市场，去时的速度是40千米/时，用了5小时送到，返回时只用了4小时，返回时的速度是多少？
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">40 * (5/4)</gadget>
<output>50</output>

<result>50</result>