In the following number series, only one number is incorrect. Select the…

Concept. In a "find the wrong term" number series, the rule is a relation the terms are built on rather than a property of any single term — most commonly the successive differences between consecutive terms, though ratios, powers, or digit operations can carry it instead. Whenever those first differences themselves form an arithmetic progression, the whole series is fixed by its opening term together with that difference rule, so every later term is forced and can be rebuilt independently of what is printed.

Application. Here the differences are meant to be consecutive even numbers rising by 2 each time: +4, +6, +8, +10, +12, +14, +16. Rebuilding the series from the opening term 56 gives:

1. 56 + 4 = 60

2. 60 + 6 = 66

3. 66 + 8 = 74, but the printed series carries 70 at this place

4. 74 + 10 = 84

5. 84 + 12 = 96

6. 96 + 14 = 110

7. 110 + 16 = 126

Cross-check. Read the differences off the printed series directly: 4, 6, 4, 14, 12, 14, 16. Two of them break the +2 rise, and both breaks straddle the same single entry. Replacing that entry with 74 turns the difference list into the clean 4, 6, 8, 10, 12, 14, 16, so one substitution repairs both breaks at once — exactly what the stem's promise that only one number is wrong demands. Changing any other single term repairs at most one break and leaves the other standing.

Result. The number that does not belong is 70; the term at that place should be 74.