Odd man out and series

(71) Which number does not belong in the series: 20, 32, 44, 56, 70, 84, 100?

• (a) 32
• (b) 44
• (c) 70
• (d) 100

Answer

Correct Answer: (d) 100
The pattern is adding 12 to each number: 20, 32, 44, 56, 68, 80, 92, …
The number 100 does not fit this pattern.

(72) Look at this series: 2, 3, 5, 9, 17, … What number should fill the blank?

• (a) 25
• (b) 33
• (c) 21
• (d) 33

Answer

Correct Answer: (d) 33
This is a series where each number is doubled and then increased by 1: 2, 2×2+1, 3×2+1, 5×2+1, 9×2+1, …
The next number should be \(17×2+1 = 33\).

(73) Which number does not belong in the series: 9, 27, 63, 135, 279, 567, 1131?

• (a) 63
• (b) 135
• (c) 279
• (d) 1131

Answer

Correct Answer: (d) 1131
The pattern is multiplying each number by 3 and then subtracting 6: 9, 9×3-6, 27×3-6, 63×3-6, 135×3-6, …
The number 1131 does not fit this pattern.

(74) Look at this series: 8, 13, 21, 34, 55, … What number should fill the blank?

• (a) 87
• (b) 64
• (c) 89
• (d) 89

Answer

Correct Answer: (d) 89
This is a Fibonacci series, where each number is the sum of the previous two: 8, 13, 21, 34, 55, 89, …
The next number should be \(55 + 34 = 89\).

(75) Which number does not belong in the series: 12, 18, 24, 36, 48, 60, 72?

• (a) 18
• (b) 24
• (c) 48
• (d) 72

Answer

Correct Answer: (d) 72
The pattern is adding 6 to each number: 12, 18, 24, 30, 36, 42, 48, …
The number 72 does not fit this pattern.