Question

Radii of the circles are given below, find their areas.
(1) 28 cm (2) 10.5 cm (3) 17.5 cm

Answer 1

$\textbf{area of circle}=\pi r^2$
here r is the radius of circle .

(1) radius of circle , r = 28cm
so, area of circle = πr² = 22/7 × 28 × 28
= 22 × 4 × 28 = 22 × 112
= 2464 cm²

(2) radius of circle , r = 10.5 cm = 21/2 cm
so, area of circle = πr² = 22/7 × 21/2 × 21/2
= 22 × 3/2 × 21/2 = 11 × 3 × 21/2
= 33 × 21/2 = 346.5 cm²

(3) radius of circle , r = 17.5 cm = 35/2 cm
so, area of circle = πr² = 22/7 × 35/2 × 35/2
= 22 × 5/2 × 35/2
= 11 × 5 × 35/2 = 55 × 35/2
= 962.5 cm²

Answer 2

Step-by-step explanation:

area of circle=πr

2

here r is the radius of circle .

(1) radius of circle , r = 28cm

so, area of circle = πr² = 22/7 × 28 × 28

= 22 × 4 × 28 = 22 × 112

= 2464 cm²

(2) radius of circle , r = 10.5 cm = 21/2 cm

so, area of circle = πr² = 22/7 × 21/2 × 21/2

= 22 × 3/2 × 21/2 = 11 × 3 × 21/2

= 33 × 21/2 = 346.5 cm²

(3) radius of circle , r = 17.5 cm = 35/2 cm

so, area of circle = πr² = 22/7 × 35/2 × 35/2

= 22 × 5/2 × 35/2

= 11 × 5 × 35/2 = 55 × 35/2

= 962.5 cm²

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