Find the one which does not belong to that group ?
Answer: D
In three of the numbers, the first two digits add to the third.
\[ 358: \; 3 + 5 = 8 \quad\checkmark \qquad 246: \; 2 + 4 = 6 \quad\checkmark \]
\[ 134: \; 1 + 3 = 4 \quad\checkmark \qquad 862: \; 8 + 6 = 14 \neq 2 \quad\times \]
So 862 does not belong.
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Find out the wrong number in the series. 2880, 480, 92, 24, 8, 4, 4
Answer: B
The divisor falls by one at each step.
\[ 2880 \div 6 = 480 \quad\checkmark \qquad 480 \div 5 = 96 \quad\text{not } 92 \]
\[ 96 \div 4 = 24 \quad\checkmark \qquad 24 \div 3 = 8 \quad\checkmark \]
\[ 8 \div 2 = 4 \quad\checkmark \qquad 4 \div 1 = 4 \quad\checkmark \]
So 92 is the wrong number; it should be 96.
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Find out the wrong number in the series. 15, 16, 34, 105, 424, 2124, 12756
Answer: D
2nd term = (1st term) x 1 + 1 = 15 x 1 + 1 = 16.
3rd term = (2nd term) x 2 + 2 = 16 x 2 + 2 = 34.
4th term = (3th term) x 3 + 3 = 34 x 3 + 3 = 105.
5th term = (4th term) x 4 + 4 = 105 x 4 + 4 = 424
6th term = (5th term) x 5 + 5 = 424 x 5 + 5 = 2125
6th term should 2125 instead of 2124.
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Find out the wrong number in the given sequence of numbers. 582, 605, 588, 611, 634, 617, 600
Answer: A
The series alternates between adding 23 and subtracting 17.
\[ 582 + 23 = 605 \quad\checkmark \]
\[ 605 - 17 = 588 \quad\checkmark \]
\[ 588 + 23 = 611 \quad\checkmark \]
\[ 611 - 17 = 594 \quad\text{but the series shows } 634 \]
So 634 is wrong; it should be 594. The rest then follow: \( 594 + 23 = 617 \) and \( 617 - 17 = 600 \).
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Insert the missing number 3, 7, 6, 5, 9, 3, 12, 1, 15, (....)
Answer: C
Two series are interleaved and run in opposite directions.
\[ \text{positions 1, 3, 5, 7, 9: } 3,\; 6,\; 9,\; 12,\; 15 \quad (+3) \]
\[ \text{positions 2, 4, 6, 8, 10: } 7,\; 5,\; 3,\; 1,\; \mathbf{-1} \quad (-2) \]
The tenth term belongs to the falling series:
\[ 1 - 2 = -1 \]
Nothing in the rule stops the second series going negative, which is what makes \( -1 \) the answer rather than 3.
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Find out the wrong number in the series. 3, 7, 15, 27, 63, 127, 255
Answer: C
Each term is double the previous plus one.
\[ 3 \to 7 \to 15 \to 31 \to 63 \to 127 \to 255 \]
The fourth term should be \( 15 \times 2 + 1 = 31 \), not 27.
So 27 is wrong. Every correct term is \( 2^{n} - 1 \), and 27 is not.
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Find the one which does not belong to that group ?
Answer: B
Three of the four numbers are perfect squares.
\[ 16 = 4^{2}, \qquad 36 = 6^{2}, \qquad 64 = 8^{2} \]
\[ 28 = 2^{2} \times 7 \text{, which lies between } 25 \text{ and } 36 \]
So 28 does not belong.
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Find the one which does not belong to that group ?
Answer: B
Take the letter positions and the differences between them:
QOR steps back two instead of one, so it breaks the pattern; QPS would fit. Note that YXA is consistent once the alphabet is allowed to wrap from Z round to A.
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Find out the wrong number in the series 3, 7, 15, 39, 63, 127, 255, 511
Answer: C
Each term is double the previous plus one.
\[ 3 \to 7 \to 15 \to 31 \to 63 \to 127 \to 255 \to 511 \]
The fourth term should be \( 15 \times 2 + 1 = 31 \), not 39.
So 39 is wrong. Every term is \( 2^{n} - 1 \), and 39 is not one less than a power of two.
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Find the one which does not belong to that group ?
Answer: C
All four use two 4s and two 2s, so look at how they are arranged.
In 4422, 2442 and 2244 the like digits sit together as pairs.
In 4242 they alternate, so no two identical digits are adjacent.
So 4242 does not belong.
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