Odd man out and series

(66) Which number does not belong in the series: 7, 11, 17, 23, 31, 37, 41?

• (a) 17
• (b) 23
• (c) 31
• (d) 41

Answer

Correct Answer: (d) 41
The pattern is prime numbers: 7, 11, 17, 23, 31, 37, 41, …
All other numbers are prime except for 41.

(67) Look at this series: 5, 9, 17, 33, 65, … What number should fill the blank?

• (a) 129
• (b) 81
• (c) 67
• (d) 129

Answer

Correct Answer: (d) 129
This is a series where each number is multiplied by 2 and then increased by 1: 5, 5×2+1, 9×2+1, 17×2+1, 33×2+1, …
The next number should be \(65×2+1 = 130+1 = 129\).

(68) Which number does not belong in the series: 14, 28, 42, 56, 70, 84, 98?

• (a) 42
• (b) 56
• (c) 70
• (d) 98

Answer

Correct Answer: (d) 98
The pattern is adding 14 to each number: 14, 28, 42, 56, 70, 84, 98, …
The number 98 does not fit this pattern.

(69) Look at this series: 6, 13, 28, 57, 120, … What number should fill the blank?

• (a) 240
• (b) 256
• (c) 280
• (d) 241

Answer

Correct Answer: (d) 241
This is a series of numbers where each number is multiplied by 2 and then increased by 1: 6, 6×2+1, 13×2+1, 28×2+1, 57×2+1, …
The next number should be \(120×2+1 = 241\).

(70) Which number does not belong in the series: 11, 17, 27, 41, 59, 77, 101?

• (a) 27
• (b) 41
• (c) 59
• (d) 101

Answer

Correct Answer: (d) 101
The pattern is adding consecutive prime numbers: 6, 10, 14, 18, 22, 26, …
The number 101 does not fit this pattern.