Question

find the circumference of a circle whose diameter is 42 centimetre

Answer 1

Diameter = 42cm
2r = 42 cm
r = 21cm
Circumference of circle = 2 × pie × r
=> 2 × 21 × 22/7
=> 2 × 3 × 22
=> 132cm

Answer 2

The circumference of a circle whose diameter is 42 centimetre is 132 centimetre

Given :

The diameter of a circle is 42 centimetre

To find :

The circumference of the circle

Formula :

For a circle of radius r unit the circumference of the circle = 2πr unit

Solution :

Step 1 of 2 :

Find radius of the circle

Here it is given that the diameter of a circle is 42 centimetre

The radius of the circle

= r

= 42/2 centimetre

= 21 centimetre

Step 2 of 2 :

Find circumference of the circle

The circumference of the circle

= 2πr centimetre

$\displaystyle \sf{ = 2 \times \frac{22}{7} \times 21 \: \: centimetre }$

$\displaystyle \sf{ = 132 \: \: centimetre }$