Question

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

Answer 1

$\huge\underline{\bf \orange{Aηsωeя :}}$

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 is 42 cm

To find -

The area of circle

Solution -

As we know that,

Circumference of circle = $2 \times pi \times r$

where, r is a radius of circle.

Put the given values in these formula we get

$42 = 2\pi \times r$

$\frac{42}{2\pi} = r$

$\frac{21}{\pi} = r$

The value of π is 3.14 .

$\frac{21}{3.14} = r$

$r = 6.68$

So,

Radius is 6.68 cm.

Area of circle = $\pi {r}^{2}$

Put the value of r we get

Area of circle = $\pi \times {6.68}^{2}$

Square means multiply the given values with itself twice.

$6.68 \times 6.68 = 44.62$

Square of 6.68 is 44.62

Area of circle = $\pi \times 44.62$

The value of π is 3.14.

Area of circle = $3.14 \times 44.62$

Area of circle = $140.1$

Hence,

Area of circle is 140.1 ${cm}^{2}$