Question

Find the radius of the sphere whose surface area is 154cm

Answer 1

$4\pi {r}^{2} = 154 \\ \pi {r}^{2} = 154 \div 4 \\ \pi {r}^{2} = 77 \div 2 \\ 22 \div 7 \times {r}^{2} = 77 \div 2 \\ {r}^{2} = (7 \times 7) \div 2 \times 2 \\ {r}^{2} = 49 \div 4 \\ r = 7 \div 2 \\ r = 3.5cm$

Answer 2

$\Huge{\underline{\underline{\mathfrak{ Solution \colon }}}}$

Given :-

Surface area of sphere is 154 cm^2

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Surface area of sphere =154 cm^2

$⟹ \: 4\pi\text{{r}}^{2} = 154 \text{cm}$

$⟹ \: 4 \times \frac{22}{7} \times \text{ {r}}^{2} = 154$

$⟹ \text{ {r}}^{2} = \bold{ \frac{ \cancel{154} \: \times \: 7}{4 \: \times \cancel{ \: 22}} }$

$⟹ \text{r} = \frac{7}{2} \times \frac{7}{2} = 3.5 \text{cm}$

Hence ,Radius of a sphere is 3.5 cm