Odd man out and series

(46) Which number does not belong in the series: 2, 4, 8, 16, 64, 128, 256?

• (a) 4
• (b) 16
• (c) 64
• (d) 256

Answer

Correct Answer: (c) 64
This is a series where each number is a power of 2: 2^1, 2^2, 2^3, 2^4, 2^6, 2^7, 2^8, …
The number 64 is not a power of 2 in this sequence.

(47) Look at this series: 1, 3, 8, 18, 38, … What number should fill the blank?

• (a) 46
• (b) 58
• (c) 68
• (d) 78

Answer

Correct Answer: (d) 78
This is the same series as Question 42. It’s a series where each number is multiplied by 2 and then increased by 2: 1, 3, 8, 18, 38, …
The next number should be \(38 \times 2 + 2 = 78\).

(48) Which number does not belong in the series: 13, 21, 33, 49, 69, 93, 121?

• (a) 21
• (b) 33
• (c) 69
• (d) 93

Answer

Correct Answer: (c) 69
The pattern is adding consecutive square numbers: 1^2, 2^2, 3^2, 4^2, 5^2, 6^2, 7^2, …
The number 69 does not fit this pattern.

(49) Look at this series: 2, 6, 24, 120, 720, … What number should fill the blank?

• (a) 1440
• (b) 144
• (c) 360
• (d) 5040

Answer

Correct Answer: (d) 5040
This is a series where each number is multiplied by the next natural number: 2*1, 2*2, 2*3, 2*4, 2*5, 2*6, …
The next number should be \(2 \times 7 = 14\).

(50) Which number does not belong in the series: 7, 14, 28, 56, 112, 224, 448?

• (a) 14
• (b) 28
• (c) 112
• (d) 224

Answer

Correct Answer: (d) 224
The pattern is doubling each number: 7, 14, 28, 56, 112, 224, 448, …
The number 224 does not fit this pattern.