In each of the following number series only one number is wrong. Find out the…
2025
In each of the following number series only one number is wrong. Find out the wrong number.
3, 12, 8, 19, 13, 32, 18, 42, 23, 52
- A.
12
- B.
19
- C.
42
- D.
32
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Correct answer: B
Key idea: split the sequence into two alternating subsequences (terms in odd positions and terms in even positions).
Odd-position subsequence (positions 1,3,5,7,9): 3, 8, 13, 18, 23 — increases by +5 each time.
Even-position subsequence (positions 2,4,6,8,10): 12, 19, 32, 42, 52 — should increase by +10 each time, but 19 does not fit this pattern.
Fix: replace the incorrect even-position term with a value that makes the even subsequence have a constant difference of +10.
Replacing 19 with 22 gives the even-position subsequence 12, 22, 32, 42, 52, which increases by +10 each time, as required.
Answer: the wrong number in the original series is 19; it should be 22.