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A balloon which always remains spherical, has a variable diameter 32(5x+7)\frac{3}{2}(5x+7). Then the rate of change of its volume with respect to x is

Solution

✅ Correct Option: 4

The balloon has a diameter of 32(5x+7)\frac{3}{2}(5x+7).

The radius is half the diameter:

r=12×32(5x+7)r = \frac{1}{2} \times \frac{3}{2}(5x+7)

r=34(5x+7)r = \frac{3}{4}(5x+7)


The volume of a sphere is:

V=43πr3V = \frac{4}{3}\pi r^3

Substituting r=34(5x+7)r = \frac{3}{4}(5x+7):

V=43π[34(5x+7)]3V = \frac{4}{3}\pi \left[\frac{3}{4}(5x+7)\right]^3

V=43π×2764(5x+7)3V = \frac{4}{3}\pi \times \frac{27}{64}(5x+7)^3

V=108192π(5x+7)3V = \frac{108}{192}\pi(5x+7)^3

V=916π(5x+7)3V = \frac{9}{16}\pi(5x+7)^3


Differentiating with respect to xx using the chain rule:

dVdx=9π16×3(5x+7)2×5\frac{dV}{dx} = \frac{9\pi}{16} \times 3(5x+7)^2 \times 5

dVdx=135π16(5x+7)2\frac{dV}{dx} = \frac{135\pi}{16}(5x+7)^2


The rate of change of volume with respect to xx is:

dVdx=135π16(5x+7)2\frac{dV}{dx} = \frac{135\pi}{16}(5x+7)^2

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