Two concentric circles are of radii $\displaystyle 4$ cm and $\displaystyle 3$ cm. Find the length of the chord of the larger circle which touches the smaller circle.

Here $\displaystyle O B=3 \mathrm{~cm}, O A=4 \mathrm{~cm}$ \[\begin{array}{l} O B \perp A C \\ \therefore A B=\sqrt{4^{2}-3^{2}}=\sqrt{7} \mathrm{~cm} \\ \text { Hence } A C=2 \sqrt{7} \mathrm{~cm} \end{array} \]SECTION-B