Odd man out and series

(11) Which number does not belong in the series: 16, 25, 49, 64, 81, 121, 144?

• (a) 49
• (b) 121
• (c) 64
• (d) 25

Answer

Correct Answer: (d) 25
This is a series of perfect squares: 4^2, 5^2, 7^2, 8^2, 9^2, 11^2, \ldots
The number 25 does not follow this pattern.

(12) Look at this series: 4, 10, 22, 46, 94, 190, … What number should fill the blank?

• (a) 382
• (b) 386
• (c) 378
• (d) 382

Answer

Correct Answer: (d) 382
This is a series of doubling and adding 2.
4 \times 2 + 2, 10 \times 2 + 2, 22 \times 2 + 2, 46 \times 2 + 2, 94 \times 2 + 2, \ldots
The next number should be \( 190 \times 2 + 2 = 382 \).

(13) Which number does not belong in the series: 13, 17, 23, 29, 31, 37, 41?

• (a) 31
• (b) 23
• (c) 37
• (d) 41

Answer

Correct Answer: (c) 37
The pattern is prime numbers: 13, 17, 23, 29, 31, 37, 41 are all prime numbers except 37.

(14) Look at this series: 1, 2, 6, 24, 120, 720, … What number should fill the blank?

• (a) 5040
• (b) 40320
• (c) 5040
• (d) 362880

Answer

Correct Answer: (c) 5040
This is a series of factorials: 1!, 2!, 3!, 4!, 5!, 6!, \ldots
The next number should be \( 7! = 5040 \).

(15) Which number does not belong in the series: 6, 12, 24, 36, 48, 72, 96?

• (a) 24
• (b) 36
• (c) 72
• (d) 48

Answer

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