## 9 Nov 2016

### Practice Sets on Quantitative Aptitude (Probability) | IBPS PO Mains Spl – Download in PDF

Practice Sets on Quantitative Aptitude (Probability) | IBPS PO Mains Spl – Download in PDF:
Dear Readers, Here we have given the important practice set questions on Quantitative Aptitude (Probability), aspirants those who are preparing for the examination can also download in pdf and make use of it.

1). A bag contains 2 yellow, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?
a)   1/2
b)   10/21
c)   9/11
d)   7/11
e)   8/11

2). Three coins are tossed. What is the probability of getting at most two tails?
a)   7/8
b)   1/8
c)   1/2
d)   1/7
e)   2/7

3). A bag contains 4 black, 5 yellow and 6 green balls. Three balls are drawn at random from the bag. What is the probability that all of them are yellow?
a)   2/91
b)   1/81
c)   1/8
d)   2/81
e)   1/91

4). In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green?
a)   1/3
b)   3/4
c)   7/19
d)   8/21
e)   9/21

5). In a class, there are 15 boys and 10 girls. Three students are selected at random. The probability that 1 girl and 2 boys are selected, is:
a)   21/46
b)   25/117
c)   1/50
d)   3/25
e)   None of these

6). 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)   1/10
b)   2/5
c)   2/7
d)   5/7
e)   3/7

7). From a pack of 52 cards, two cards are drawn together at random. What is the probability of both the cards being kings?
a)   1/15
b)   25/57
c)   35/256
d)   1/221
e)   17/225

8). A bag contains 4 white, 5 red and 6 blue balls. Three balls are drawn at random from the bag. The probability that all of them are red, is:
a)   1/22
b)   3/22
c)   2/91
d)   2/77
e)   3/77

9). One card is drawn at random from a pack of 52 cards. What is the probability that the card drawn is a face card (Jack, Queen and King only)?
a)   1/13
b)   3/13
c)   1/4
d)   9/52
e)   None of these

10). 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)   3/4
b)   4/7
c)   1/8
d)   3/7
e)   None of these

1)   2)   3)   4)   5)   6)   7)   8)   9)   10)

Solutions:
1. B) Total number of balls = 2 + 3 + 2 = 7
Let S be the sample space.
n(S) = Total number of ways of drawing 2 balls out of 7 = 7C2
Let E = Event of drawing 2 balls , none of them is blue.
n(E) = Number of ways of drawing 2 balls , none of them is blue
= Number of ways of drawing 2 balls from the total 5 (=7-2) balls = 5C2
(∵ There are two blue balls in the total 7 balls. Total number of non-blue balls = 7 - 2 = 5)
P(E) = n(E)/n(S) = 5C2/7C2 = (5 x 4)/(7 x 6) = 10/21
2. A) Total number of outcomes possible when a coin is tossed = 2 (∵ Head or Tail)
Hence, total number of outcomes possible when 3 coins are tossed, n(S) = 2 × 2 × 2 = 8
(∵ i.e., S = {TTT, TTH, THT, HTT, THH, HTH, HHT, HHH})
E = event of getting at most two Tails = {TTH, THT, HTT, THH, HTH, HHT, HHH}
Hence, n(E) = 7
P(E) = n(E)/n(S) = 7/8
3. A) Total number of balls = 4 + 5 + 6 = 15
Let S be the sample space.
n(S) = Total number of ways of drawing 3 balls out of 15 = 15C3
Let E = Event of drawing 3 balls, all of them are yellow.
n(E) = Number of ways of drawing 3 balls, all of them are yellow
= Number of ways of drawing 3 balls from the total 5 = 5C3
(∵ there are 5 yellow balls in the total balls)
P(E) = n(E)/n(S) = 5C2/15C2 = 2/91
4. A) Total number of balls = (8 + 7 + 6) = 21.
Let E  = event that the ball drawn is neither red nor green
= event that the ball drawn is blue.
n(E) = 7.
Therefore, P(E) = 7/21 = 1/3
5. A) Let S be the sample space and E be the event of selecting 1 girl and 2 boys.

6. C) P (getting a prize) = 10/(10 + 25) = 10/35 = 2/7
7. B) Clearly, n(S) = (6 x 6) = 36.
Let E = Event that the sum is a prime number.
Then E         = { (1, 1), (1, 2), (1, 4), (1, 6), (2, 1), (2, 3), (2, 5), (3, 2), (3, 4), (4, 1), (4, 3), (5, 2), (5, 6), (6, 1), (6, 5) }
n(E) = 15.
P(E) = 15/36 = 5/12
8. C)

9. B) Clearly, there are 52 cards, out of which there are 12 face cards.
P (getting a face card) = 12/52 = 3/13
10. B) Let number of balls = (6 + 8) = 14.
Number of white balls = 8.
P (drawing a white ball) = 8/14 = 4/7