Using a CalculatorEdexcel GCSE Maths: Revision notes

A scientific calculator can perform the four operations, along with fractions, powers, roots and standard form, but only if button sequences are entered correctly and results interpreted carefully.

Key skills:

• Use the fraction button (usually shown as a stacked box) to enter and simplify fractions directly, including mixed numbers
• Use the power button (xʸ or ^) for powers, and the root button (√ or ˣ√y) for roots, including cube roots and higher
• Use brackets to control the order of operations, especially in multi-step calculations
• Use the standard form button (×10ˣ or EXP) to enter and read numbers in standard form

Calculators can display results in unexpected formats, so it is important to interpret the screen correctly:

• A fraction may display as a stacked fraction rather than a decimal — convert if the question requires a decimal or percentage
• A recurring decimal may be shown truncated (e.g. 0.333333333) — recognise this as 1/3 and use exact fraction form where required
• Standard form may appear as '5.6ᴇ06' or '5.6×10⁰⁶' on screen — this must be written correctly as 5.6 × 10⁶ in working, not copied as displayed
• Negative numbers and negative indices must be entered with the correct negative/minus key, which differs from the subtraction key on many calculators

After calculating, always check the answer is sensible:

1. Estimation check — round the original values to 1 significant figure and calculate roughly by hand; compare to the calculator answer
2. Inverse operation check — reverse the calculation (e.g. if you multiplied, divide the answer back) to confirm you return to the starting value

This catches common calculator input errors, such as missing brackets or a mistyped digit.

Calculators are used to substitute values into formulae and evaluate trigonometric functions (sin, cos, tan and their inverses) in context problems, such as finding a missing side or angle in a right-angled triangle.

• Always check the calculator is in the correct angle mode (degrees, not radians) for GCSE trigonometry
• When substituting into a formula, enter the whole expression using brackets to preserve the correct order of operations, rather than calculating in separate uncombined steps that could introduce rounding errors
• For multi-step problems, keep unrounded values in the calculator's memory between steps rather than re-entering a rounded value, to avoid premature rounding error