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Interview Questions on Probability
Probability - Aptitude
6.Two dice are thrown together. What is the probability that the sum of the numbers on the two faces is divisible by 4 or 6?
x
Option: D
Explanation
n(S) = {6 * 6} = 36
E = event of getting sum of the numbers on the two faces that is divisible by 4 or 6
E = {(1, 3), (1, 5), (2, 2), (2, 4), (2, 6), (3, 1), (3, 3), (3, 5), (4, 2), (4, 4), (5, 1), (5, 3), (6, 2), (6, 6)}
P(E) = n(E)/n(S) = 14/36 = 7/18
7.What is the probability of getting a sum 9 from two throws of a dice?
x
Option: A
Explanation
n(S) = {6 * 6} = 36
E = event of getting a sum of 9
E = {(3, 6), (4, 5), (5, 4), (6, 3)}
P(E) = n(E)/n(S) = 4/36 = 1/9
8.In a simultaneous throw of two dice, what is the probability of getting a doublet?
x
Option: D
Explanation
n(S) = (6 * 6) = 36
E = event of getting a doublet
E = ((1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)) = 15 +6 = 21
P(E) = n(E)/n(S) = 6/36 = 1/6
9.Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn bears a number which is a multiple of 3?
x
Option: A
Explanation
S = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}
E = event of getting a multiple of 3
E = {3, 6, 9, 12, 15, 18}
P(E) = n(E)/n(S) = 6/20 = 3/10
10.In a lottery, there are 10 prizes and 25 blanks. A lottery is drawn at random. What is the probability of getting a prize?
x
Option: A
Explanation
n(S) = {10 + 35} = 45
E = event of getting a prize
n(E) = 10
P(E) = n(E)/n(S) = 10/45 = 2/7
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