In each series, one term is wrong. Find the wrong term in the series below.…

Concept

In an alternating (interleaved) number series, the terms at odd positions form one arithmetic progression and the terms at even positions form a separate arithmetic progression. Within each progression the common difference stays constant, so the wrong term is the single value that breaks the constant step of its own progression.

Application

Split the series 110, 115, 120, 120, 100, 125, 95 by position into its two interleaved progressions:

1. The even-position progression 115, 120, 125 increases by a constant +5, so it is intact and acts as the anchor.

2. The odd-position progression should therefore also have a constant step. Reading from the two end values, 110 down to 95 over three steps gives a constant step of -5, i.e. the intended progression is 110, 105, 100, 95.

3. Comparing actual odd-position terms 110, 120, 100, 95 with the intended 110, 105, 100, 95, the third-position value 120 is the only mismatch; it should be 105.

So the wrong term is 120 (the value appearing at the third position); replacing it with 105 makes the odd progression a clean -5 sequence.

Cross-check

With 120 corrected to 105 the full series reads 110, 115, 105, 120, 100, 125, 95: the odd-position terms are 110, 105, 100, 95 (step -5) and the even-position terms are 115, 120, 125 (step +5). Both progressions now have a constant step, confirming 120 is the term that was wrong.