Uncle Lin spent 6 hours driving from place A to place B, traveling 50km per hour, and spent 4 hours on the return trip. How many kilometers per hour did he travel on the return trip?
林叔叔开车从甲地到乙地一共用了6小时，每小时行50km，返回时用了4小时，返回时每小时行多少km？
<gadget id="calculator">6 / 4</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">50 * (3/2)</gadget>
<output>75</output>

<result>75</result>