Question

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

Answer 1

$\huge\boxed{\fcolorbox{purple}{ink}{Answer}}$

Given that:-

Circumference is 42 cm

We need the RADIUS

We need the area

Concept:-

Surface area, 2D figures

Let's Do!

Perimeter = 2 × pi × r

$42 = 2 \times \frac{22}{7} \times r$

$\dfrac{42 \times 7}{2 \times 22} = r$

Radius = 6.681 cm.

Now, Area = pi × r²

$\dfrac{22}{7} \times \dfrac{42 \times 7}{2 \times 22}$

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

Answer:

circumference = 2πr

42 = 2πr

42/2 =πr

21 *7/22 = r

r=6.6

area = πr^2

= 22/7*(6.6)^2

=21 cm^2