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The Grade 12 Formula Rosetta Stone

Tap or hover any variable below to reveal exactly what it means — and the specific mistake markers see most often around it.

Financial Mathematics

Tap or hover a variable to see its meaning and trap.

A = P(1 + i)^n

Annuities — Present vs Future Value

Same-looking formulas, completely different use case. Mixing them up is one of the most common Paper 1 errors.

Present Value (loans, mortgages)

P_v = \dfrac{x\left[1 - (1+i)^{-n}\right]}{i}

Future Value (sinking funds, retirement)

F_v = \dfrac{x\left[(1+i)^n - 1\right]}{i}

⚠️ Timing warning: check whether the first payment happens in 1 month (standard) or immediately (upfront) — this shifts n by one period and is a favourite trick in exam questions.

Calculus — First Principles

The single most common way to lose method marks on this topic.

f'(x) = \lim_{h \to 0} \dfrac{f(x+h) - f(x)}{h}

⚠️ Trap: you must write

\lim_{h \to 0}

on every single line of your working until h actually cancels out — dropping it early costs you the method mark even if your final answer is correct.

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