Two circles with centres $O$ and $N$ touch each other at point $P$ as shown. $O, P$ and $N$ are coll

Question

Two circles with centres $O$ and $N$ touch each other at point $P$ as shown. $O, P$ and $N$ are collinear. The radius of the circle with centre $O$ is twice that of the circle with centre N.OX is a tangent to the circle with centre $N$, and $O X=18 \mathrm{~cm}$.\   What is the radius of the circle with centre $N$ ?\

Professor PC Thomas Classes · Answer

(c): $\frac{9}{\sqrt{2}} \mathrm{~cm}$