100+ Probability Aptitude Questions and Answers - 1

Question: 1

In a simultaneous throw of a two dice, what is the probability of getting a doublet?

(A) \$\${1}/{2}\$\$

(B) \$\${1}/{4}\$\$

(C) \$\${1}/{6}\$\$

(D) \$\${2}/{3}\$\$

Ans: C

In a simultaneous throw of two dice, n(S) = (6 × 6) = 36.

Let E = event of getting a doublet = {(1, 1), (2, 2), (3, 3), (4, 4), (5,5), (6,6)}

∴ P(E) = \$\${n(E)} / {n(S)}\$\$ = \$\${6} / {36}\$\$ = \$\${1} /{6}\$\$.

Question: 2

One card is drawn at random from a pack of 52 cards. What is the probability that the card drawn is a face card?

(A) \$\${1} / {4}\$\$

(B) \$\${1} / {13}\$\$

(C) \$\${4} / {13}\$\$

(D) \$\${9} / {52}\$\$

Ans: C

Clearly, there are 52 cards, out of which there are 16 face cards.

∴ P (getting a face card) = \$\${16} / {52}\$\$ = \$\${4} / {13}\$\$.

Question: 3

A box contains 4 red, 5 green and 6 white balls. A ball is drawn at random from the box. What is the probability that the ball drawn is either red or green?

(A) \$\${1} / {5}\$\$

(B) \$\${2} / {5}\$\$

(C) \$\${3} / {5}\$\$

(D) \$\${7} / {15}\$\$

Ans: C

Total number of balls = (4 + 5 + 6) = 15.

P(drawing a red ball or a green ball)

= P(red) + P(green) = \$\$({4} /{15} + {5} /{15})\$\$ = \$\${9}/{15}\$\$ = \$\${3} / {5}\$\$.

Question: 4

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?

(A) \$\${1}/{2}\$\$

(B) \$\${2}/{5}\$\$

(C) \$\${3}/{10}\$\$

(D) \$\${3}/{20}\$\$

Ans: C

Here, S = {1, 2, 3, 4, ……., 19, 20}.

Let E = event of getting a multiple of 3 = {3, 6, 9, 12, 15, 18}.

∴ P (E) = \$\${n(E)} / {n(S)}\$\$ = \$\${6} / {20}\$\$ = \$\${3} /{10}\$\$.

Question: 5

A bag contains 6 black and 8 white balls. One ball is drawn at random. What is the probability that the ball drawn is white?

(A) \$\${1} / {8}\$\$

(B) \$\${3} / {4}\$\$

(C) \$\${3} / {7}\$\$

(D) \$\${4} / {7}\$\$

Ans: D

Total number of balls = (6 + 8) = 14.

Number of white balls = 8.

P(drawing a white ball) = \$\${8} /{14}\$\$ = \$\${4} / {7}\$\$.

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