Question

The sum of circumference and the radius of a circle is $51cm$, find the radius of the circle.

Answer 1

Sum of circumference and radius = 51 cm.

Find radius = (?)

$\to$ circumference + radius = 51

$\therefore 2\pi r+r=51$

$\therefore r(2\pi +1)=51$

$\therefore r=\frac{51}{2\pi +1}$

$=\frac{51}{2\times \frac{22}{7}+1}$

$=\frac{51}{\frac{44+7}{7}}$

$=\frac{51\times 7}{51}$

$\therefore r=7cm$