Answer:
b = 4.6 ft
h = 2.3 ft
Step-by-step explanation:
The volume of the tank is given by:
[tex]b^2*h=49[/tex]
Where 'b' is the length of the each side of the square base, and 'h' is the height of the tank.
The surface area can be written as:
[tex]A=b^2+4bh\\A=b^2+4b*({\frac{49}{b^2}})\\A=b^2+\frac{196}{b}[/tex]
The value of b for which the derivate of the expression above is zero is the value that yields the minimum surface area:
[tex]\frac{dA}{db} =0=2b-\frac{196}{b^2}\\2b^3=196\\b=4.61\ ft[/tex]
The value of h is then:
[tex]h=\frac{49}{4.61^2}\\h=2.31\ ft[/tex]
Rounded to the nearest tenth, the dimensions are b = 4.6 ft and h = 2.3 ft.
