Quantitative Ability - Odd Man Out and Series

Directions to Solve
Find out the wrong number in the series:

Question 1)
190, 166, 145, 128, 112, 100, 91

A) 100

B) 166

C) 145

D) 128

E) 112

Answer - Option D

Solution:
Go on subtracting 24, 21, 18, 15, 12, 9 from the numbers to get the next number.
190 - 24 = 166
166 - 21 = 145
145 - 18 = 127 [Here, 128 is placed instead of 127]
127 - 15 = 112
112 - 12 = 100... and son on.
Therefore, 128 is wrong

Question 2) 

1, 3, 10, 21, 64, 129, 356, 777

A) 10

B) 21

C) 64

D) 129

E) 356

Answer - Option E

Solution:

A x 2 + 1, B x 3 + 1, C x 2 + 1, D x 3 + 1  and son on. So, 356 is wrong.

Question 3)

6, 12, 48, 100, 384, 768, 3072

A) 768

B) 384

C) 100

D) 48

E) 12

Answer - Option C

Solution:

Each even term of the series is obtained by multiplying the previous term by 2.
2^nd term = (1^st term) x 2 = 6 x 2 = 12

4^th term = (3^rd term) x 2 = 48 x 2 = 96

6^th term = (5^th term) x 2 = 384 x 2 = 768

Therefore, 4^th term should be 96 instead of 100

Question 4)

40960, 2560, 640, 200, 40, 10

A) 640

B) 40

C) 200

D) 2560

E) 10240

Answer: Option C

Solution:

Go on diving by 4 to get the next number. So, 200 is wrong.

Question 5)

10, 26, 74, 218, 654, 1946, 5834

A) 26

B) 74

C) 218

D) 654

E) 1946

Answer: option D

Solution:

2^nd term = (1^st term) * 3-4 = 10*3-4 = 26.

3^rd term = (2^nd term) * 3-4 = 26*3-4 = 74.

4^th term = (3^rd term) * 3-4 = 74*3-4 = 218.

5^th term = (4^th term) * 3-4 = 218*3-4 = 650.

Thus, 5^th term must be 650 instead of 654

Question 6)

15, 16, 34, 105, 424, 2124, 12576

A) 16

B) 34

C) 105

D) 424

E) 2124

Answer:  Option E

Solution:

2^nd term = (1^st term) * 1+1 = 15*1+1 = 16.

3^rd term = (2^nd term) * 2+2 = 16*2+2 = 34.

4^th term = (3^rd term) * 3+3 = 34*3+3 = 105.

5^th term = (4^th term) * 4+4 =105*4+4 = 424.

6^th term = (5^th term) * 5+5 = 424*5+ 5 = 2125

Therefore, 6^th term should 2125 instead of 2124

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