# Quantitative Aptitude: Probability Questions – Set 14

1. There are 5 boys and 3 girls. A group of 3 members is to be made. Find the probability that either there are 2 boys and 1 girl or 2 girls and 1 boy?
45/56
44/54
49/64
52/58
None of these
Option A
2 boy and 1 girl, prob. = 5C2*3C1/8C3
2 girl and 1 boy, prob. = 5C1*3C2/8C3

2. A carton contains 8 black and 7 grey balls. 2 balls are drawn one by one without replacement. What is the probability that the balls are alternately of different colors?
7/10
8/15
9/14
10/15
None of these
Option B
When 1st is black, probability = 8/15 * 7/14
When 1st is grey, probability = 7/15 * 8/14

3. A carton contains 10 electric lights from which 2 lights are defective. Two lights are chosen at random. What is the probability that one of them is defective?
11/43
14/45
16/45
15/35
None of these
Option C
Probability=2C1*8C1/10C2

4. A bag contains 8 black and 7 grey balls. A ball is drawn out of it and put back in the bag. Then a ball is drawn again. What is the probability that both the balls are grey?
49/225
48/125
25/95
55/235
None of these
Option A

5. A bag contains 8 black and 7 grey balls. 2 balls are drawn one by one without replacement. What is the probability that the balls are alternately of different colors?
3/14
10/12
8/15
7/15
6/15
Option C
When 1st is black, probability= 8/15 * 7/14
When 1st is grey, probability = 7/15 * 8/14

6. A bag 5 ruby and 8 white balls.Two draws of three balls each are made.What is the probability that the balls were ruby in the first draw and white in the second draw ?
140/20449
145/20445
20550/150
Cannot be determined
None of these
Option A
5C3/13C3 *8C3/13C3

7. The ratio of the number of womens to the number of mens is 5 : 2 in a class of 21 persons. A group of three students is to to be selected at random amongst them. What is the probability that the selected group of persons contain one mens and two womens?
51/260
45/266
40/55
37/255
None of these
Option B
n(S) =21C3 = 1330
n(E) =15C1 × 6C2 = 15 × 15 = 225
Probability = 225/1330 = 45/266

8. A bag contains 4 weige, 8 beige and 6 blue balls. If two balls are drawn at random, find the probability of both the balls being beige?
15/154
25/152
28/253
27/250
None of these
Option C
n(S) =18C2 =153
n(E) = 28
P(E) = 28 /153 = 28/153

9. In a shelf, there are 7 Computer, 6 Maths and 5 CA books. One book is picked up randomly. What is the probability that it is neither in Computer nor in CA ?
1/5
1/8
1/3
1/7
None of these
Option C
Probability=6/18

10. If two dices are thrown simultaneously, what is probability that sum of numbers appeared is less than 7?
5/12
7/12
9/14
10/15
None of these
Option A

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