Answer:
0.8 ft³/min
Step-by-step explanation:
Assuming that the cross section formed by the water at a depth of x is b. Then, if we use the property of similar triangles we have...
See the attachment for the workings.
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Continuation of the workings
From the question, we're told that the water is 6 inches deep. Converting this inch to ft, we have
6 ft = 0.5 ft.
So we use 0.5 as our x, and then use 12 ft³/min as our dV/dt. Doing this, we have
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12 = 30 * 0.5 dx/dt
12 = 15 dx/dt
dx/dt = 12/15
dx/dt= 0.8 ft³/min
