Learn and practice Problems on probablity with easy explaination and shortcut tricks. All questions and answers on probablity covered for various Competitive Exams

Solve Problems:

1) What is the probability of getting an even number when a dice is rolled?

The sample space when a dice is rolled, S = (1, 2, 3, 4, 5 and 6) So, n (S) = 6 E is the event of getting an even number. So, n (E) = 3 So, the probability of getting an even number P (E) = = 3/6 = 1/2

2) What is the probability of getting two tails when two coins are tossed?

The sample space when two coins are tossed = (H, H), (H, T), (T, H), (T, T) So, n(S) = 4 The event “E” of getting two tails (T, T) = 1 So, n(E) = 1 So, the probability of getting two tails, P (E) = =n(E)/n(S) = 1/4

3) The tickets numbered from 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket has a number which is a multiple of 3 or 5?

The sample space, S= (1, 2, 3, 4, 5 …18, 19, 20) or n(S) = 20

The event “E” of getting a multiple of 3 or 5 = (3, 6, 9, 12, 15, 18, 5, 10, 20) or n (E) = 9 So, the probability of getting multiple of 3 or 5, P (E) = = 9/20

4) A box contains 2 red, 3 green, and 2 blue balls. What is the probability that none of the balls drawn is blue?

Total number of balls = (2+3+2) = 7 Let S be the sample space. Then, n (S) = the total number of ways of drawing two balls out of 7: = ^{7}C_{2} =(7*6)/(2*1) =21

Let E is the event of drawing 2 balls, none of which is blue.

n (E) = number of ways of drawing 2 balls out of (2+3) balls.

= ^{5}C_{2}

=(5*4)/(2*1)= 10

P(E) =n(E)/n(S) =10/21

5) In a bag, there are 8 red, 7 yellow and 6 green balls. If one ball is picked up at random, what is the probability that it is neither red nor green?

Total number of balls or sample space = 8 + 7+ 6 = 21 So, n(S) = 21 Let E is the event that ball drawn is neither red nor green or event that the ball drawn is yellow. There are 7 yellow balls: So, n (E) = 7

Try to solve more Problems on probablity.

6) What is the probability of getting a sum 5 from two throws of a dice?

In two throws a dice, n (S) = 6 * 6 = 36 Let E is the event of getting a sum of five. E = (1, 4), (4, 1), (2, 3), (3, 2) So, n (E) = 4 So, P (E) = = 4/36 or 1/9

7) A man throws two dice simultaneously on the floor. What is the probability of getting two numbers whose product is even?

8) In a group of students, there are 15 boys and 10 girls. If three students are selected at random, what is the probability that 1 girl and 2 boys are selected?