A car drives from Jiajia to City B. It travels at a speed of 51 kilometers per hour for 4 hours, and travels for 6 hours when it returns. What is the speed of this car when it returns?
一辆汽车从加成开往乙城，去时以每小时51千米的速度行驶了4小时，返回时行驶了6小时，这辆汽车返回时的速度是多少？
<gadget id="calculator">4 / 6</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">51 * (2/3)</gadget>
<output>34</output>

<result>34</result>