Question

The difference between circumference and diameter of a circle is 21.4 CM find the radius of the circle

Answer 1

Circumference of a Circle = 2πr
$= 2 \times \frac{22}{7} \times r$
And Radius = r
Hence, Diameter = 2r

So when we subtract Circumference with Diameter, we will get the value of r. As, in the equation formed is -

$2\pi \: r - 2r$
$= 2 \times \frac{22}{7} \times r - 2r$
Therefore, this value will be equal to 21.4 cm

$2 \times \frac{22}{7} \times r - 2r = \frac{214}{10}$
$\frac{44}{7} r - 2r = \frac{214}{10}$

Multiple both sides by 7


$7 \times \frac{44}{7} - 2r = \frac{214}{10} \times 7$

$44r - 2r = \frac{214 \times 7}{10}$

$42r = \frac{214 \times 7}{10}$

$r = \frac{214 \times 7}{10 \times 42}$
Simplify the fraction.

$\frac{749}{150} \: or \: 4.993$