## Probability

#### Probability

1. What is the probability that a number selected from the numbers 1, 2, 3, 4, 5....16 is a prime number ?
1. 1/16
2. 5/8
3. 3/8
4. 7/16

1. S = {1, 2, 3, ......16}
E = {2, 3, 5, 7, 11, 13}
∴ P(E) = n(E)/n(S) = 6/16= 3/8

##### Correct Option: C

S = {1, 2, 3, ......16}
E = {2, 3, 5, 7, 11, 13}
∴ P(E) = n(E)/n(S) = 6/16= 3/8

1. An urn contains 9 red, 7 white and 4 black balls. A ball is drawn at random. What is the probability that the ball drawn is not red ?
1. 1/11
2. 9/20
3. 2/11
4. 11/20

1. P (red) = 9 / (9 + 7 + 4) = 9/20

##### Correct Option: D

P (red) = 9 / (9 + 7 + 4) = 9/20
∴ P(not-red) = (1 - 9/20) = 11/20

1. In a lottery there are 20 prizes and 15 blanks. What is the probability of getting prize ?
1. 1/10
2. 2/5
3. 4/7
4. 2/7

1. P (getting a prize ) = 20 / (20 + 15 ) = 20 / 35 = 4/7

##### Correct Option: C

P (getting a prize ) = 20 / (20 + 15 ) = 20 / 35 = 4/7

1. The odds in favour of an event are 3 : 5. The probability of occurrence of the event is ?
1. 3/5
2. 3/8
3. 1/3
4. 1/5

1. Number of cases favourable of E = 3
Total Number of cases = (3 + 5 ) = 8
∴ P(E) = 3/8

##### Correct Option: B

Number of cases favourable of E = 3
Total Number of cases = (3 + 5 ) = 8
∴ P(E) = 3/8

1. The probability of getting heads in both trials when a balanced coin is tossed twice will be ?
1. 1/4
2. 1/2
3. 1
4. 3/4

1. Probability of getting head in one trail = 1/2
∴ Reqd Probability of getting heads in both the trails = 1/2 x 1/2 = 1/4

##### Correct Option: A

Probability of getting head in one trail = 1/2
∴ Reqd Probability of getting heads in both the trails = 1/2 x 1/2 = 1/4