Question

A bag contains 20 balls marked 1 to 20 .One ball is drawn at random from the bag.What is the probability that the ball drawn is marked with a number which is a multiple of 5 or 7.

Answer 1

P=no of required outcome/total no of possible outcome
=6/20=3/10

Answer 2

P(E) =4/20=1/5 (for 5)
P(E) =2/20=1/10(for 7)
4/20+2/20=6/20
                =3/10