Calculate the surface area of a sphere with radius 10 cm. Use $π = 22/7$ .

hard 5 marks Class 5 · Mathematics · Does it Look the Same

Answer

8800/7 cm²

The correct answer is 8800/7 cm² — Thus the surface area is $\frac{8800}{7}, cm^{2}$ , which is approximately $1257.14, cm^{2}$ .

Step-by-step solution

Recall that the surface area of a sphere is given by $S = 4 p i r^{2}$ .
Substitute $r = 10$ : $S = 4 p i (10)^{2} = 4 p i c d o t 100$ .
Use $π = 22/7$ : $S = 4 \cdot \frac{22}{7} \cdot 100 = \frac{88}{7} \cdot 100$ .
Multiply: $\frac{88}{7} \cdot 100 = \frac{8800}{7}$ .
Thus the surface area is $\frac{8800}{7}, cm^{2}$ , which is approximately $1257.14, cm^{2}$ .

Common mistake: Using

4 p i r

instead of

4 p i r^{2}

Concept tested: Surface area of sphere