Odd man out and series

(16) Which number does not belong in the series: 3, 6, 12, 24, 48, 96, 192?

• (a) 12
• (b) 48
• (c) 12
• (d) 96

Answer

Correct Answer: (c) 12
This is a series of doubling numbers: 3, 6, 12, 24, 48, 96, 192, …
The number 12 does not fit this pattern.

(17) Look at this series: 1, 3, 9, 27, 81, 243, … What number should fill the blank?

• (a) 321
• (b) 486
• (c) 729
• (d) 729

Answer

Correct Answer: (d) 729
This is a series of powers of 3: 3^0, 3^1, 3^2, 3^3, 3^4, 3^5, \ldots
The next number should be \(3^6 = 729\).

(18) Which number does not belong in the series: 11, 17, 23, 29, 37, 41, 47?

• (a) 23
• (b) 29
• (c) 37
• (d) 47

Answer

Correct Answer: (d) 47
The pattern is prime numbers: 11, 17, 23, 29, 37, 41, 47 are all prime numbers except 47.

(19) Look at this series: 5, 12, 27, 58, 121, 244, … What number should fill the blank?

• (a) 500
• (b) 244
• (c) 500
• (d) 500

Answer

Correct Answer: (d) 500
This is a series of numbers where each number is doubled and then increased by a square number: 5 \times 2 + 2^2, 12 \times 2 + 3^2, 27 \times 2 + 4^2, \ldots
The next number should be \(244 \times 2 + 5^2 = 500\).

(20) Which number does not belong in the series: 7, 14, 21, 28, 36, 42, 49?

• (a) 14
• (b) 21
• (c) 28
• (d) 36

Answer

Correct Answer: (d) 36
The pattern is adding 7 to each number: 7, 14, 21, 28, 35, 42, 49, …
The number 36 does not fit this pattern.