Question

The circumference of circle is 42cm. Find the radius of the circle and area of the circle.​

Answer 1

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Perimeter = 2 × pi × r

22/7 ×r

2×22/42×7 = r

Radius = 6.681 cm.

Now, Area = pi × r²

=> 22/7 × 2×22/42×7

DID nothing, just replaced the values.

So, the required area is 21 cm².

Keep a special vigil on units.

If not, convert and solve them.

Use simplification before decimal conversion.

In the area, I used the RADIUS 1st value, and the calculation was made super easy.

Answer 2

Given,

Circumference of circle = 42 cm

2πr = 42

r = 42 / 2π

r = 42*7/(22*2)

r = 6.68 cm

Now,

Area of circle = πr²

                       = 22/7 * 6.68 * 6.68 = 140.11 cm²