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What is the probability that a number selected from the numbers 1, 2, 3,…….,25 is a prime number, when each of the given numbers is equally likely to be selected? 
A) 8/25 B) 9/25 C) 1/25 D) 2/25 Correct Answer : 9/25 Explanation : Let S be the sample space. Let E be the event space= event that the number selected is a prime number = {2, 3, 5, 7, 11, 13, 17, 19, 23} Probability of occurrence of event, P(E) = n(E)/n(S) = 9/25 
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Find the probability that a leap year selected at random will contain 53 Sundays.  
A) 5/7
B) 3/4
C) 4/7
D) 2/7
Correct Answer : 2/7 Explanation : Total number of days in a leap year = 366  
There are 5 red and 7 blue balls in a bucket. If one ball is drawn at random from the bucket then what is the probability that the ball drawn will be of red colour?  
A) 5/12
B) 7/12
C) 1/2
D) 1/12
Correct Answer : 5/12 Explanation : total numbers of balls in bucket = 5 red+7 blue=12  
Two dices are thrown randomly. Find the probability of getting the sum of digits as 9.  
A) 1/6
B) 1/9
C) 1/12
D) None of these
Correct Answer : 1/9 Explanation : All possible outcome when two dices are thrown randomly =sample space is n(S)=(6*6)=36 outcomes  
A bag contains 2 red marbles, 3 green marbles and 4 blue marbles. A marble is picked at random from the bag. What is the probability that the marble is not a blue marble?  
A) 4/9
B) 5/9
C) 1/9
D) 2/3
Correct Answer : 5/9 Explanation : total numbers of marbles in bag = 2 red+3 green+4 blue=9  
A coin is tossed. What is the probability of getting a head or a tail?  
A) 0
B) 1
C) 1/2
D) 1/4
Correct Answer : 1 Explanation : When coin is tossed, result will be either heads or tails.there Total number of possible outcomes i.e. sample space n(S) : {H,T} = 2 So number of probable outcomes and total number of outcomes are same i.e. 2. So, probability of getting either heads or tails when a coin is tossed once Note:  
In a box there are 4 black, 4 orange and 2 blue marbles. Two marbles are drawn at random. What is the probability that at least one marble is of blue colour?  
A) 4/5
B) 3/5
C) 1/5
D) None of these
Correct Answer : None of these Explanation : total numbers of marbles in box= 4 black+4 orange+2 blue=10 marbles  
 
An box 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 ?  
A) 1/11 B) 9/20 C) 2/11 D) 11/20 Correct Answer :11/20 Explanation : total numbers of balls in bucket =9 red + 7 white + 4 black=20
 
A number is chosen at random among the first 120 natural numbers. The probability of the number chosen being a multiple of 5 or 15 is ?  
A) 1/5 B) 1/8 C) 1/6 D) 1/12 Correct Answer :1/5 Explanation : sample space n(S)=number of ways chosen at random among the first 120 natural numbers=>120  
A single letter is selected at random from the word 'PROBABILITY' . The probability that it is a vowel, is ?  
A) 3/11 B) 4/11 C) 2/11 D) 1/11 Correct Answer :4/11 Explanation : sample space n(S)=Total number of letters=>11 Hence probability p(E)=n(E)/n(S)=4/11  
 
If a number is chosen from the set {1, 2, 3…90}, then the probability that the chosen number is multiple of 7 is  
A) 1/6
B) 2/15
C) 1/12
D) 7/30
Correct Answer : 2/15 Explanation : All possible outcome If a number is chosen from the set {1, 2, 3…90} =sample space is n(S)=90 ways  
A number is randomly selected from set A ={1,2,3,} and then second number is randomly selected from set B={1,3,9} The probability that the sum of the two numbers selected will be less than or equal to 4, is:  
A) 1/3
B) 5/9
C) 2/3
D) 7/9
Correct Answer : 1/3 Explanation : All possible outcome to select the number from both set and when do sum =sample space is n(S)={1+1,1+3,1+9,2+1,2+3,2+9,3+1,3+3,3+9}=9 ways  
Which of the following has the maximum probability to be the sum of the number on top face of two dice, when both the dice thrown together?  
A) 7
B) 8
C) 9
D) 10
Correct Answer : 7 Explanation : Outcomes for Two Dice
the maximum probability to be the sum of the number on top face of two dice = maximum Outcomes for that number 7 =(6, 1) , (5, 2), (4, 3), (3, 4), (2, 5), (1, 6) Hence ,maximum probability that the sum of the two dice is seven  
Two unbiased coins are tossed. What is probability of getting at most one tail ?  
A) 5/4
B) 3/4
C) 1
D) 1/2
Correct Answer : 3/4 Explanation : Sample space , n(S) = {HH, TT, TH, HT} = 4 Probability P(E) = n(E)/n(S) = 3 / 4  
Three unbiased coins are tossed, what is the probability of getting at least 2 tails ?  
A) 1/3
B) 1/4
C) 1/2
D) 3/2
Correct Answer : 1/2 Explanation : Sample space ,n(S) = {TTT, HHH, TTH, THT, HTT, THH, HTH, HHT} = 8 Probability P(E) = n(E)/n(S) = 4 / 8  
In a throw of dice what is the probability of getting number greater than 5 ?  
A) 2/6
B) 1/2
C) 5/6
D) 1/6
Correct Answer : 1/6 Explanation : Sample space ,n(S) = {1, 2, 3, 4, 5, 6} = 6 Probability P(E) = n(E)/n(S) = 1/ 6  
There are 3 children in the Khanna's family and it is known that there is at least 1 girl among the 3 children. What is the probability that all 3 of them are girls?  
A) 1/7
B) 1/8
C) 1/6
D) 2/7
Correct Answer : 1/7 Explanation : Let G=girl, B=boy. thus sample space is, n(S) : {GGG,GGB,GBG,BGG,GBB,BGB,BBG} = 7 Therefore, probability that all will be girl = n(E)/n(S) = 1/7  