U is inversely proportional to the cube of V and U = 81 when V…

U is inversely proportional to the cube of V and U = 81 when V = 2. Find U when V = 3

Correct Answer: Option A

Explanation

U (propto frac{1}{V^3})
U = (frac{k}{V^3})
k = UV(^3)
k = 81 x 2(^3) = 81 x 8
When V = 3,
U = (frac{k}{V^3})
U = (frac{81 times 8}{3^3})
U = (frac{81 times 8}{27}) = 24

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