A ship travels from A to B, traveling 25 kilometers per hour along the current, and 15 kilometers per hour against the current. It takes 4 hours to go back and forth. How many kilometers are there between A and B?
轮船从甲地到乙地，顺水每小时行25千米，逆水每小时行15千米，来回一次共行4小时，甲乙两地相距多少千米？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">25 + 15</gadget>
<output>40</output>

<gadget id="calculator">60 / 40</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">25 * (3/2)</gadget>
<output>75/2 = around 37.5</output>

<result>75/2 = around 37.5</result>