Question

find the circumference of a circle whose diameter is 21 CM

Answer 1

since the diameter of circle is 21 cm so....
radius is 21/2 cm ...
circumference is 2Πr hence ...
which is 2×22/7×21/2= 66 cm
hope this helps

Answer 2

Given,

Diameter of the circle = 21 cm

To find,

Circumference of the circle

Solution,

Now, we have the diameter and we know that radius is half the diameter.

Radius = Diameter/2

$r = \frac{d}{2}$

$r = \frac{21}{2}$

r = 10.5 cm

Therefore , the radius of the circle is 10.5 cm.

Circumference of the circle = $2\pi r$

= $2*\frac{22}{7}*10.5$

$\frac{21*22}{7} = 22*3 \\\\=66$

Circumference of the circle will be 66 cm

Hence, the circumference of the circle with diameter as 21 cm will be 66 cm.