Question

Find the diameter of a circle whose circumference is equal to the some of circumference of circle with radii $10cm,12cm$,and $18cm$

Answer 1

Let d be the required diameter, then radius of the circle $\frac{d}{2}$

It is given that,

$2\pi \frac{d}{2}=2\pi \left(10\right)+2\pi \left(12\right)+2\pi \left(18\right)$

$\Rightarrow 2\pi \left(\frac{d}{2}\right)=2\pi (10+12+18)$

$\Rightarrow \frac{d}{2}=40$

$\Rightarrow d=80cm$.