# Surface Areas & Volumes | Exercise 13.4 | Q2

###### CBSE Class 9 Maths | NCERT SolutionS to Exercise | Surface Area of sphere

Question 2: Find the surface area of a sphere of diameter:

(i) 14 cm
(ii) 21 cm
(iii) 3.5m

## NCERT Solution to Class 10 Maths

### Explanatory Answer | Exrecise 13.4 Question 2

Radius of the sphere, r = $$frac{d}{2}$ = $\frac{21}{2}$ cm Surface area of sphere = 4 × π × r2 Take π = $\frac{22}{7}$ Surface area of sphere = 4 × $\frac{22}{7}$ × $\frac{21}{2}$ × $\frac{21}{2}$ = 22 × 3 × 21 = 1386 cm2 #### Part$iii): Diameter of the sphere, d = 3.5 m

Radius of the sphere, r = $\frac{d}{2}$ = $\frac{3.5}{2}$ m
Surface area of sphere = 4 × π × r2
Take π = $\frac{22}{7}$
Surface area of the sphere = 4 × $\frac{22}{7}$ × $\frac{3.5}{2}$ × $\frac{3.5}{2}$
= 22 × 0.5 × 3.5
= 38.5 m2

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