A car delivers goods from A to B with an average speed of 57 km/h and takes 4 hours. It is much faster to return than to go, and it takes 1 hour less. What is the average speed of this car when it returns?
一辆汽车从甲地送货到乙地，去时平均速度为57千米每小时，共用4小时．返回时比去时快多了，少用1小时，这辆车返回时的平均速度是多少？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<gadget id="calculator">57 * (4/3)</gadget>
<output>76</output>

<result>76</result>