It is known that it takes 4 hours for a ship to travel 48 kilometers downstream and 6 hours to travel 48 kilometers upstream. Now the ship travels from upstream port A to downstream port B. It is known that the length of the waterway between the two ports is 72 kilometers. When the boat is sailing, a passenger throws a wooden board into the water from the window. When the boat arrives at port B, how far is the wooden board from port B?
已知一艘轮船顺水行48千米需4小时，逆水行48千米需6小时．现在轮船从上游A港到下游B港．已知两港间的水路长为72千米，开船时一旅客从窗口扔到水里一块木板，问船到B港时，木块离B港还有多远？
<gadget id="calculator">48 / 4</gadget>
<output>12</output>

<gadget id="calculator">72 / 12</gadget>
<output>6</output>

<gadget id="calculator">48 / 6</gadget>
<output>8</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">72 - 12</gadget>
<output>60</output>

<result>60</result>