Odd Man Out & Series Questions and Answers

Answer: D

Every number here is prime except one.

\[ 41,\; 43,\; 47,\; 53,\; 61,\; 71,\; 73 \;\text{are prime} \]

\[ 81 = 3^{4} = 3 \times 27 \]

So 81 is the odd man out. Its digit sum is 9, so it is divisible by 3 - the fastest way to spot it.

Answer: B

The multiplier grows by one at each step.

\[ 2 \times 2 = 4,\quad 4 \times 3 = 12,\quad 12 \times 4 = 48,\quad 48 \times 5 = 240 \]

\[ 240 \times 6 = \mathbf{1440} \]

Assuming a constant multiplier of 5 would give 1200, and of 4 would give 960 - the first option.

Answer: B

Three of the four are perfect cubes.

\[ 343 = 7^{3}, \quad 1331 = 11^{3}, \quad 2197 = 13^{3} \]

\[ 121 = 11^{2} \text{, a square rather than a cube} \]

So 121 does not belong. It is deliberately paired with 1331, the cube of the same number 11.

Answer: C

Each number is a perfect square.

\[ 1,\; 4,\; 9,\; 16,\; 36,\; 49 = 1^{2},\, 2^{2},\, 3^{2},\, 4^{2},\, 6^{2},\, 7^{2} \]

\[ 20 \text{ is not a square} \]

So 20 breaks the run. Note that \( 5^{2} = 25 \) is missing from the list, and 20 has been slipped in where it would have stood.

Answer: B

In each group the two digits, read together, give the letter's position in the alphabet.

• 1P6: P is the 16th letter, and the digits read 16 ✓
• 2T0: T is the 20th letter, and the digits read 20 ✓
• 1R8: R is the 18th letter, and the digits read 18 ✓
• 2Y4: Y is the 25th letter, but the digits read 24 ✗

So 2Y4 does not belong.

Answer: B

Three of the four numbers are odd.

\[ 3,\; 5,\; 9 \;\text{are odd}; \qquad 4 \;\text{is even} \]

So 4 does not belong. The list avoids making them all prime - 9 is \( 3^{2} \) - so oddness, not primality, is the shared property.

Answer: B

Three of the four words end in the same three letters.

\[ \text{P-art}, \quad \text{C-art}, \quad \text{D-art} \]

Each is a single letter followed by -art.

Trap does not fit that shape - it is an anagram of "part" rather than a member of the -art family.

Answer: D

Walk, talk and drink are verbs - each names an action.

Plank is a noun, a flat length of timber.

So Plank does not belong. The rhyme with "walk" and "talk" is the distraction; the grammatical class is the real grouping.

Answer: C

Every term should be a multiple of 11.

\[ 22,\; 33,\; 66,\; 99,\; 121,\; 594 \;\text{are all divisible by 11} \]

\[ 279 \div 11 = 25.36 \ldots \]

So 279 is the wrong number. The alternating-sum test confirms it: \( 2 - 7 + 9 = 4 \), which is not a multiple of 11.

Answer: B

Each number is a perfect square.

\[ 1 = 1^{2},\; 4 = 2^{2},\; 9 = 3^{2},\; 16 = 4^{2},\; 25 = 5^{2},\; 36 = 6^{2} \]

\[ 23 \text{ lies between } 16 \text{ and } 25 \text{ and is not a square} \]

So 23 is the odd man out.