An arithmetic sequence increases by a constant difference. Example: 2, 5, 8, 11 (common difference = 3).
nth term: a_n = a₁ + (n-1)d. Sum of n terms: S_n = n/2 × (2a₁ + (n-1)d)
This tool is most valuable when you need a result to compare against something else: a quoted figure, a competing option, or a budget threshold. Accurate comparisons require accurate inputs and arithmetic — this calculator ensures both.
The most frequent error is rounding intermediate values before completing the full calculation. Round only the final result — rounding intermediate steps compounds errors in multi-step calculations, sometimes significantly.
A student checks their overall module grade before results day: 3 assignments scored 72%, 68%, and 81% — the calculator confirms the weighted average and tells them what score they would need on the final exam to achieve a target grade.
A sequence where each term is formed by adding a constant (common difference d) to the previous term.
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