Question 515110
We can compute the volume of the tank (it is a cylindrical tank) with the information given, so we'll end up with cubic ft of tank capacity.  And a gallon is unit of volume liquid measurement; but we need the conversion for gallons to cubic feet to answer the question.  We can look that up.  
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First, the area (A) of the top of the tank is given by the equation:
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A = Pi * r^2
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From info given:
r = 5
h = 7
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The volume (V) of the cylindrical tank is given by the equation:
V = (Pi * r^2) * height (h)
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V = 3.14159*(5^2)*7 in cu ft.
V = 549.78 cu ft
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We look up the conversion factor for cu ft to gallons:
1 cu ft = 7.48 gal
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Then multiply the volume of the tank, V, by the conversion factor for gallons:
V = 549.78 cu ft * 7.48 gal/cu ft
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cu ft cancel out and we are left with
V = 4,112.34 gal fit in our cylindrical tank
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cheers, Lee