In the following question, select the missing number from the given series.…

Concept: A number series can be built by interleaving two independent alternating sub-sequences — the terms sitting at the odd positions (1st, 3rd, 5th, 7th, ...) follow their own arithmetic pattern, and the terms at the even positions (2nd, 4th, 6th, ...) follow a separate arithmetic pattern. To find a missing term, split the series into these two position-groups and identify each group's own step size.

1. Split the series by position: odd positions give 43, 42, 41, ?; even positions give 45, 46, 47.

2. Odd-position terms 43, 42, 41 form a decreasing run: 43 - 1 = 42 and 42 - 1 = 41.

3. Even-position terms 45, 46, 47 form an increasing run: 45 + 1 = 46 and 46 + 1 = 47 - confirming the even-position pattern holds steadily across the series.

4. Apply the same odd-position step to the last known odd-position term: 41 - 1 = 40.

Cross-check: Placing 40 as the 7th term extends the odd-position run to 43, 42, 41, 40, a consistent arithmetic progression with the same step size already seen between the earlier odd-position terms.

So the missing number in the series is 40.