Never round in the middle. Keep the full, unrounded value on your calculator throughout (using the ANS key or memory), and round only the final answer.

Cambridge's default rounding conventions (unless the question says otherwise):

• Non-exact numerical answers → 3 significant figures.
• Angles → 1 decimal place.

Without brackets, a calculator only divides by the first term after the division sign. Always enclose a multi-term numerator or denominator in brackets.

Example: calculate $\dfrac{6.4^2 - 3.9}{\sqrt{2.5+1.3}}$, to 3 significant figures.

1. Enter as (6.4^2 - 3.9) ÷ √(2.5 + 1.3), with brackets around both the numerator and the contents of the root.
2. Read the full display: $16.994558\ldots$
3. Round only at the end: $17.0$ (3 s.f.).

A calculator doesn't know it's showing money or time — you have to translate the display yourself.

Example: a calculator shows $3.4$ after dividing hours worked by days. To convert to hours and minutes: the whole number ($3$) is the hours, and the decimal ($0.4$) must be multiplied by $60$ to give minutes: $0.4 \times 60 = 24$. So the answer is $3$ hours $24$ minutes.

Calculators have two different-looking minus symbols: a small (-) button for typing a negative number, and the longer − subtraction button. Using the wrong one can silently change your answer.

Example: find $(-5)^2 - (-2)^3$ using a calculator.

1. Enter the first term as ( (-) 5 ) ^ 2 — using the negative-number button, with brackets around the whole base — giving $25$.
2. Enter the second term as ( (-) 2 ) ^ 3, giving $-8$.
3. Combine using ordinary subtraction: 25 − (−8) = $25+8=33$.

• Rounding at each intermediate step instead of carrying the exact value through to the end.
• Reading a decimal time display as minutes directly, without multiplying the decimal part by $60$.
• Omitting brackets around a multi-term numerator or denominator, which silently changes what the calculator actually computes.