Question

A box contains 20 balls bearing numbers 1,2,3,4, ------,20. A ball is

drawn at random from the box. What is the probability that the
number on the ball is:
1. an odd no.
2. divisible by 2 or 3
3. prime number
4. not divisible by 10​

Answer 1

Answer:

1. Odd no. = favourable outcomes = 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19

Probability = favourables outcomes/ total outcomes = 10/20 = 1/2

2. No. divisible by 2 or 3 = favourable outcomes = 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20

Probability = favourable outcomes/total outcomes = 13/20

3. Prime no. = favourable outcomes = 2, 3, 5, 7, 11, 13, 17, 19

Probability = favourable outcomes/total outcomes = 8/20 = 2/5

4. No. not divisible by 10 = favourable outcomes = 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19

Probability = favourable outcomes/total outcomes = 18/20 = 9/10