The Fibonacci sequence: 1, 1, 2, 3, 5, 8, 13, 21... Each number is the sum of the two before it.
F(10) = 55. F(20) = 6,765. The ratio of consecutive Fibonacci numbers approaches the golden ratio φ ≈ 1.618.
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.
A common mistake is applying the formula in the wrong direction — particularly with percentage and ratio problems, where the part and the whole can be mistakenly swapped. Check which value is the reference (the 'whole') before entering inputs.
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.
F(20) = 6,765.
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