The radii of two circles are 5cm and 12cm. The area of a third circle is equal to the sum of the area of the two circles. The radius of the third circle is :
13 cm
21 cm
30 cm
17 cm
Correct Option: A
Using Rule 14, πr² = π × 5² + π × 12² ⇒ r² = 25 + 144 = 169 ⇒ r = √169 = 13 cm
