Question

Two concentric circles are of diameters 30 cm and 18 cm. Find the length of the chord of the larger circle which touches the smaller circle.

Answer 1

In the diagram AB is the chord touching the smaller circle. 

We have the right angled triangle OO'B

By Pythagoras theorem

Now since the chord of the larger circle which touches the smaller circle is bisected at the point of contact

We have

AB = 2 × 24 = 48 cm

So ans is 18 cm.