Question

Two circles having radii $3.5cm$ and $4.8cm$ touch each other internally. Find the distance between their centres.

Answer 1

Let the two circles having centres $P$ and $Q$ touch each other internally at point $R$. Here, $QR=3.5cm,PR=4.8cm$
The two circles touch each other internally.
$\therefore$ By theorem of touching circles,
$$\begin{array}{cc}& P-Q-R\\ & PQ=PR-QR\\ & =4.8-3.5\\ & =1.3cm\end{array}$$
[The distance between the centres of circles touching internally is equal to the difference in their radii]