Look at the series, 77, 70, 63, 56, 49, _, which number should come next?

Concept: In a subtraction-type arithmetic number series, each term is formed by adding the same constant difference to the previous term. To predict the next term, first find that constant difference from the terms already given, then apply it once more to the last given term.

1. Find the difference between the first two consecutive terms: 70 minus 77 equals -7.

2. Confirm the same difference recurs across the rest of the series: 63 minus 70 equals -7; 56 minus 63 equals -7; 49 minus 56 equals -7.

3. Since the common difference is consistently -7, apply it once more to the last given term: 49 + (-7) = 42.

Cross-check using the general term of an arithmetic sequence, T(n) = 77 - 7(n - 1). For the 6th term, T(6) = 77 - 7(5) = 77 - 35 = 42, which independently confirms the result.

So the number that should come next in the series is 42.