pool has an inlet pipe at the top and an outlet pipe at the bottom. If only the inlet pipe is opened, the pool can be filled in 50 minutes; if only the outlet pipe is opened, a pool of water can be drained in 60 minutes. Now there is a crack parallel to the bottom of the pool in a certain position in the middle. If only the outlet pipe is opened It takes 80 minutes for the water inlet pipe to fill a pool of water, but it only takes 46.5 minutes to fill a pool of water with only the outlet pipe open. Excuse me: at what fraction of the height does the crack appear from the bottom of the pool?
一个水池，顶部有一个进水管，底部有一个出水管．如果只打开进水管，50分钟可以把水池灌满；如果只打开出水管，60分钟可以把一池水放完，现在水池在中间的某个位置出现了一条与池底平行的裂缝，如果只打开进水管，需要80分钟才能放满一池水，而只打开出水管只需46.5分钟即可放完一池水，请问：裂缝出现在离池底几分之几高度的地方？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>