IBPS Clerk Mains 2016-17 (Important Questions-4)

IBPS Clerk Mains 2016-17 (Important Questions-4)

Directions (1-5): What will come in place of (_) in the following number series ?

1. 108, 115, 104, 117, 100, _

A. 118
B. 119
C. 120
D. 122
E. None of these

Sol. B 
Alternate series of -4 and +2.
Thus, 117 + 2 = 119.

2. 16, 17, 37, 116, _

A. 464
B. 465
C. 467
D. 468
E. None of these

Sol. 16*1 + 1 = 17
     17*2 + 3 = 37
     37*3 + 5 = 116
    116*4 + 7 = 471.

3. 13, 17, 33, 97, _, 1377

A. 373
B. 363
C. 353
D. 343
E. None of these

Sol. 17 - 13 = 4
     33 - 17 = 4*4 = 16
     97 - 33 = 16*4 = 64

Thus, 64*4 + 97 = 353.

4. 3, 7, 13, 25, 31, _

A. 46
B. 43
C. 40
D. 41
E. None of these

Sol. 2 + 1 = 3
     3 + 4 = 7
     4 + 9 = 13
     5 + 16= 25
     6 + 25= 31
     7 + 36= 43.

5. 1, 3, 11, 13, 29, _

A. 38
B. 34
C. 33
D. 31
E. None of these

Sol. 1 + 0 = 1
     4 - 1 = 3
     9 + 2 = 11
    16 - 3 = 13
    25 + 4 = 29
    36 - 5 = 31.   

6. A box contains 4 red balls, 5 green balls and 6 white balls. A ball is drawn at random from the box. What is the probability that the ball drawn is either red or green?

A. 2/5
B. 3/5
C. 1/5
D. 7/15
E. None of these

Sol. Required Probability = (4c1 + 5c1)/15c1 = 9/15 = 3/5.

7. 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

Sol. Ways of selecting 3 students = 25C3 = 2300
Ways of seleting 1 girl and 2 boys = 10C1 * 15C2 = 1050

Required Probability = 1050/2300 = 21/46.

8. Four persons are chosen at random from a group of 3 men, 2 women and 4 children. The chance that exactly 2 of them are children, is:

A. 1/9
B. 1/5
C. 1/12
D. 10/21
E. None of these

Sol. Favorable cases are,
1. 2 children + 2 women = 4C2 * 3C2 = 18
2. 2 children + 2 men   = 4C2 * 2C2 = 6
3. 2 children + 1 women + 1 men = 4C2 * 3C1 * 2C1 = 36

Number of favorable cases = 36 + 6 + 18 = 60
Total ways of selecting 4 persons = 9C4 = 126

Required Probability = 60/126 = 10/21.

9. A box contains 20 electric bulbs, out of which 4 are defective. Two bulbs are chosen at random from this box. The probability that at least one of these is defective, is:

A. 4/19
B. 7/19
C. 12/19
D. 21/95
E. None of these

Sol. Probability that atleast one of them is defective = 1 - (probability that none of them are defective)
Ways of selecting 2 bulbs = 20C2 = 190.
Ways of selecting 2 non-defective bulbs = 16C2 = 120.

Probability that both are non-defecive = 120/190 = 12/19.
Thus, required probability = 1 - 12/19 = 7/19.

10. In a class, 30% of the students offered English, 20% offered Hindi and 10% offered both. If a student is selected at random, what is the probability that he has offered English or Hindi?

A. 2/5
B. 3/4  
C. 3/5
D. 3/10
E. None of these

Sol. P(E) = 30/100 = 3/10 ; P(H) = 20/100 = 1/5
P(E∩H) = 10/100 = 1/10


Thus, P(E∪H) = 3/10 + 1/5 - 1/10 = 2/5. 

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