Two concentric circles of radii 15 cm and 13 cm are given. Find the length of the chord of the larger circle which touches the smaller circle.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 4.

PQ touches the smaller circle and OM is perpendicular to QP which divides the PQ into two equal parts.
OM = 13 (radius of smaller circle)
OP = 15 (radius of bigger circle)
In right-angled OMP
⇒ (OP)2 = (OM)2 + (PM)2
⇒ 152 = 132 + (PM)2
⇒ (PM)2 = 225 - 169
⇒ PM2 = 56
⇒ PM = √56 = √7 × 2 × 2 × 2 = 2√14
Now,
⇒ PQ = 2 PM
⇒ PQ = 4√14 cm
The length of the chord which touches the smaller circle is 4√14 cm