Q:

A bag contains 6 white and 4 black balls .2 balls are drawn at random. Find the probability that they are of same colour.

A) 1/2 B) 7/15
C) 8/15 D) 1/9
 
Answer & Explanation Answer: B) 7/15

Explanation:

Let S be the sample space

Then n(S) = no of ways of drawing 2 balls out of (6+4) = \inline {\color{Black}10C_{2}} = =45

Let E = event of getting both balls of same colour

Then,n(E) = no of ways (2 balls out of six) or (2 balls out of 4)

                =\inline {\color{Black}6C_{2}+4C_{2}} = = 15+6 = 21

Therefore, P(E) = n(E)/n(S) = 21/45 = 7/15

Report Error

View Answer Workspace Report Error Discuss

74 14013
Q:

Two cards are drawn at random from a pack of 52 cards.what is the probability that either both are black or both are queen?

A) 52/221 B) 55/190
C) 55/221 D) 19/221
 
Answer & Explanation Answer: C) 55/221

Explanation:

We have n(s) = \inline {\color{Black}52C_{2}} = = 1326.

Let A = event of getting both black cards

     B = event of getting both queens

A∩B = event of getting queen of black cards

n(A) = \inline {\color{Black}26C_{2}} =  = 325, n(B)= \inline {\color{Black}4C_{2}} = = 6  and  n(A∩B) = \inline {\color{Black}2C_{2}} = 1

P(A) = n(A)/n(S) = 325/1326;

P(B) = n(B)/n(S) = 6/1326 and

P(A∩B) = n(A∩B)/n(S) = 1/1326

P(A∪B) = P(A) + P(B) - P(A∩B) = (325+6-1) / 1326 = 330/1326 = 55/221

Report Error

View Answer Workspace Report Error Discuss

33 8120
Q:

A man and his wife appear in an interview for two vacancies in the same post. The probability of husband's selection is (1/7) and the probability of wife's selection is (1/5). What is the probability that only one of them is selected ?

A) 2/7 B) 1/7
C) 3/4 D) 4/5
 
Answer & Explanation Answer: A) 2/7

Explanation:

Probability_35.jpg

Report Error

View Answer Workspace Report Error Discuss

64 7439
Q:

A problem is given to three students whose chances of solving it are 1/2, 1/3 and 1/4 respectively. What is the probability that the problem will be solved?

A) 1/4 B) 1/2
C) 3/4 D) 7/12
 
Answer & Explanation Answer: C) 3/4

Explanation:

Let A, B, C be the respective events of solving the problem and  be the respective events of not solving the problem. Then A, B, C are independent events

 are independent events

Now,  P(A) = 1/2 , P(B) = 1/3 and P(C)=1/4

 P( none  solves the problem) = P(not A) and (not B) and (not C)

                  = 

                  =                                                =  

                  = 

Hence, P(the problem will be solved) = 1 - P(none solves the problem)

                = 

Report Error

View Answer Workspace Report Error Discuss

21 7072
Q:

In a lottery, there are 10 prizes and 25 blanks. A lottery is drawn at random. What is the probability of getting a prize?

A) 2/7 B) 5/7
C) 1/5 D) 1/2
 
Answer & Explanation Answer: A) 2/7

Explanation:

Total number of outcomes possible, n(S) = 10 + 25 = 35

Total number of prizes, n(E) = 10

Report Error

View Answer Workspace Report Error Discuss

36 6762