There is a ring-shaped water tank for experiments. If the switch is activated, the water in the tank will flow at a certain speed. If the switch is not activated, the water will remain still. Put a model boat with a non-operating engine into the water in the flowing water tank. After 1 minute and 15 seconds, drive the water tank for a circle. At this time, the ship model engine starts to work automatically. , The model boat drove around the tank again. At this time, if the switch of the water tank is turned off, how long will it take for the model ship to drive around the water tank again?
有一个实验用的环形水槽，若启动开关，槽中的水就以一定速度定向流动，若不启动开关，水则静止．将一艘发动机未工作的模型船放入水中在流动的水槽中，经1分15秒，行驶水槽一圈，此时，船模发动机自动开始工作，水流的方向与船行方向一致，经25秒，船模又行驶水槽一圈．这时，若关闭水槽开关，船模再行驶水槽一圈，需要多少时间？
<gadget id="calculator">1 / 25</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">1 / 75</gadget>
<output>1/75 = around 0.013333</output>

<gadget id="calculator">(1/25) - (1/75)</gadget>
<output>2/75 = around 0.026667</output>

<gadget id="calculator">1 / (2/75)</gadget>
<output>75/2 = around 37.5</output>

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