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

### Question

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

A) 24

B) 27

C) 32

D) 36

### Explanation:

U $$\alpha \frac{1}{V^3}$$
U = $$\frac{k}{V^3}$$
k = UV3
k = 81 x 23 = 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

## Dicussion (1)

• U $$\alpha \frac{1}{V^3}$$
U = $$\frac{k}{V^3}$$
k = UV3
k = 81 x 23 = 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