From A to B, (3/5) is uphill and (2/5) is downhill. A person travels back and forth between A and B and walks a total of 10 kilometers uphill, so how many kilometers did he travel uphill when returning from B to A?
从甲地到乙地，其中(3/5)是上坡路，(2/5)是下坡路．一人在甲、乙间往返一趟，共走上坡路10千米，那么从乙地返回甲地时上坡行了多少千米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">10 * (2/5)</gadget>
<output>4</output>

<result>4</result>