Hello Aspirants. Welcome to Online Maths in AffairsCloud.com. Here we are creating question sample in **Probability**, which is common for all the competitive exams. We have included Some questions that are repeatedly asked in exams !!

**The probability of two persons of passing the interview are 1/3 and 3/5. Then calculate the probability that only one of them pass the interview ?**

a) 7/15

b) 8/15

c) 11/15

d) 13/15

Answer –**b) 8/15**

Solution :

PF + FP (P = pass, F = fail)

1/3*2/5 + 2/3*3/5 = 8/15

**Among a group of 5 boys and 6 girls, 4 members is to be selected for an event. Find the probability that at least one boy is selected ?**

a) 17/22

b) 19/22

c) 21/22

d) 15/22

Answer –**c) 21/22**

Solution :

sol = 1 – no boy is selected

1 – 6c4/11c4 = 21/22

**The probability that the problem will be solved by three persons are 1/2, 1/3 and 1/6. Find the probability that the problem is solved ?**

a) 11/18

b) 13/18

c) 15/18

d) 17/18

Answer –**b) 13/18**

Solution :

1 – 1/2*2/3*5/6 = 13/18

**A urn contains 4 red balls, 5 green balls and 6 white balls, If one ball is drawn at random, find the probability that it is neither red nor white ?**

a) 1/3

b) 1/4

c) 1/5

d) 2/3

Answer –**a) 1/3**

Solution :

5c1/15c1 = 1/3

**An elevator starts with 4 passenger and stops at 7 floors of an apartment. Find the probability that all 4 passengers travel to different floor ?**

a) 110/343

b) 120/343

c) 18/49

d) 139/343

Answer –**b) 120/343**

Solution :

Total number of outcomes = 7*7*7*7

Favourable outcome = 7*6*5*4

P = (7*6*5*4)/7*7*7*7 = 120/343

**A five digit number is formed from the numbers 1,3,5,7,8 and 9 without repeating the numbers. Find the probability that the number is divisible by 5 ?**

a) 1/4

b) 1/5

c) 1/6

d) 1/7

Answer –**c) 1/6**

Solution :

Total number of outcome = 6*5*4*3*2

Favourable outcome = 5*4*3*2. So, P = 1/6

**From a deck of 52 cards, a card is selected and without replacing the card a new card is selected. Find out the probability that the first card is an ace and second card is a king ?**

a) 4/52*3/51

b) 4/51*3/52

c) 4/52*4/51

d) 3/52*3/51

Answer-**c) 4/52*4/51**

Solution :4/52*4/51

**The probability that a person will be alive after 20 years is 1/4 and that of his wife is 2/5. Find out the probability that both are not alive after 20 years ?**

a) 7/20

b) 9/20

c) 11/20

d) 13/20

Answer –**b) 9/20**

Solution :

prob. That man is not alive = 3/4 and that of his wife = 3/5

Prob. That both will be dead = 3/4*3/5 = 9/20

**(Q 9 -10) Three coins are tossed simultaneously.**

**Find out the probability that there is at least 2 heads ?**

a) 1/2

b) 1/4

c) 1/6

d) 1/8

Answer-**a) 1/2**

Solution :

Sol = Total outcomes = {HHH,HTH,HHT,THH,TTT,TTH,THT,HTT}

Favourable outcome = HHH, HTH, HHT,THH

Prob = 4/8 = 1/2

**Find the probability that there is exactly two tails ?**

a) 3/8

b) 5/8

c)7/8

d) 1/8

Answer –**a) 3/8**

Solution :

Favourable outcome = TTH, THT, HTT

So, prob. = 3/8

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