Question

Find the surface area of a sphere of diameter (i) 14cm (ii) 21cm (iii) 3.5cm

Answer 1

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Here is your answer.

As we know the formula,

Surface Area of sphere = $4 \pi {r}^{2}$

(1) Diameter = 14cm

Radius = $\frac{d}{2}$

= 7cm

$surface \: area = 4\pi {r}^{2} \\ = \frac{4 \times 22 \times 7 \times 7}{7} \\ \\ = 616 {cm}^{2}$

(2) Diameter = 21cm

Radius

$= \frac{21}{2} cm$

$surface \: area = 4\pi {r}^{2} \\ \\ = \frac{4 \times 22 \times 21 \times 21}{7 \times 2 \times 2} \\ \\ = 1386 {cm}^{2}$
(3) Diameter = 3.5 cm

Radius

$= \frac{3.5}{2} cm$

$surface \: area = 4\pi {r}^{2} \\ \\ = \frac{4 \times 22 \times 3.5 \times 3.5}{7 \times 2 \times 2} \\ \\ = 38.5cm {}^{2}$

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