A circular ring (path) has outer radius 14 $m$ and inner radius 7 $m$ . Find the area of the ring. Use π = $\frac{22}{7}$ (answer in $m^{2}$ ).

Class 7Perimeter and AreaPerimeter and Area

Step-by-Step Solution

Ring area = π

(R^{2} - r^{2}) = \frac{22}{7} (1 4^{2} - 7^{2}) = \frac{22}{7} (196 - 49) = \frac{22}{7}

(147) = 22 \times 21 = 462 m^{2}

Answer: B) 462

**Area of a circle = π ×

r^{2}

.**

Note it's

r

squared, not

2 r

. So if

r = 7

, area = π × 49 (not π × 14).

Example

(r = 7

cm, π =

\frac{22}{7}) : A = \frac{22}{7} \times 49 = 22 \times 7 = 154 cm^{2}

.

Example

(r = 10

cm, π ≈ 3.14): A ≈

3.14 \times 100 = 314 cm^{2}

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