Question

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

Answer 1

2 π r = 42cm

2 × 22/7 × r = 42cm

r = 42×7/44 = 294/44 = 147/22cm.

π r ² = 22/7 × (147/22)² = 22/7 × 21609/484 = 3087/22 = 140.318cm².

Answer 2

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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.