Odd man out and series

(51) Which number does not belong in the series: 9, 16, 25, 36, 49, 64, 100?

• (a) 25
• (b) 36
• (c) 100
• (d) 64

Answer

Correct Answer: (c) 100
The pattern is squaring consecutive natural numbers: 3^2, 4^2, 5^2, 6^2, 7^2, 8^2, …
The number 100 does not fit this pattern.

(52) Look at this series: 1, 5, 25, 125, 625, … What number should fill the blank?

• (a) 3125
• (b) 1250
• (c) 1562
• (d) 3125

Answer

Correct Answer: (d) 3125
This is a series of numbers raised to the power of 5: 5^0, 5^1, 5^2, 5^3, 5^4, 5^5, …
The next number should be \(5^6 = 3125\).

(53) Which number does not belong in the series: 10, 20, 40, 80, 160, 320, 640?

• (a) 40
• (b) 80
• (c) 320
• (d) 640

Answer

Correct Answer: (c) 320
The pattern is doubling each number: 10, 20, 40, 80, 160, 320, 640, …
The number 320 does not fit this pattern.

(54) Look at this series: 3, 10, 21, 36, 55, … What number should fill the blank?

• (a) 78
• (b) 66
• (c) 72
• (d) 78

Answer

Correct Answer: (d) 78
The pattern is adding consecutive square numbers: 2^2, 3^2, 4^2, 5^2, 6^2, 7^2, …
The next number should be \(7^2 = 49\), and adding it to 55 gives 78.

(55) Which number does not belong in the series: 14, 26, 42, 62, 86, 114, 146?

• (a) 42
• (b) 62
• (c) 86
• (d) 114

Answer

Correct Answer: (d) 114
The pattern is adding consecutive even numbers: 12, 16, 20, 24, 28, 32, …
The number 114 does not fit this pattern.