A truck goes to a certain place to deliver goods at a speed of 45 km/h and arrives in 4 hours. The speed when returning is 60 km/h, how many hours can you return?
一辆货车去某地送货，去时的速度是45千米/时，4小时到达．回来时的速度是60千米/时，几小时可以回来？
<gadget id="calculator">4 / 60</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">45 * (1/15)</gadget>
<output>3</output>

<result>3</result>