A box contains cards numbered 3, 5, 7, 9, …, 35, 37. A card is drawn at random from the box. Find the probability that the number on the drawn card is a prime number.

A solid metallic sphere of diameter 8 cm is melted and drawn into a cylindrical wire of uniform width. If the length of the wire is 12 m, find its width.

The sum of first n terms of an A.P. is 5n² + 3n. If its m^th term is 168, find the value of m. Also find the 20^th term of this A.P.

Prove that the lengths of tangents drawn from an external point to a circle are equal.