Question: There are 3 piers next to a river, A, B, and C. It takes 2 hours for Xiao Ming to row a boat from A to C and then to B, but it takes 2.5 hours to go from B to C and finally return to A. It is known that when he is rowing, the upstream speed is 3 km/h, and the downstream speed is only 6 km/h, so how many kilometers is the distance between A and B?
问：一条河流旁依次有3个码头，甲、乙、丙，小明划船从甲地到丙地然后到乙地要2小时，而从乙地先去丙地最后返回甲地用了2.5小时，已知他划船时，逆流的速度是3千米/时，顺水的速度市6千米/时，那么甲、乙两地相距多少千米？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/3) - (1/6)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">0.5 / (1/6)</gadget>
<output>3</output>

<result>3</result>