Methods

Methods: understand before you practise

Each guide explains one idea step by step, with worked examples, common pitfalls and corrected exercises. Read the method, then practise with the quiz.

Numbers

How to calculate percentages: method, examples and pitfalls

Find 15% of a number, work out a rate, apply an increase or discount, recover an original price: the method step by step, with examples and pitfalls.

Read the guide Fractions explained: simplify, add, multiply and divide

How to simplify fractions, find a common denominator, then add, subtract, multiply and divide them, with worked examples and exercises.

Read the guide Mean, median and mode: how to calculate and when to use them

How to calculate a mean, a median, a weighted average and a mode, and how to tell which one describes your data best.

Read the guide How to solve linear equations step by step

Solve first-degree equations with one unknown: isolate x, handle brackets and fractions, check your answer, with examples and exercises.

Read the guide

Practise with the quiz: Numbers →

Logic

Binary numbers: convert and add them by hand

How binary counting works, how to convert to and from decimal, how to add binary numbers and read hexadecimal, with exercises.

Read the guide

Practise with the quiz: Logic →

Science

Ohm’s law and electric power, with worked examples

Use V = I × R and P = V × I, combine resistors in series and parallel, and avoid unit mistakes, with worked examples and exercises.

Read the guide

Practise with the quiz: Science →

Geometry

Volume formulas: cube, box, cylinder, cone and sphere

The formulas for the volume of a cube, box, cylinder, cone and sphere, how to convert to litres and the mistakes to avoid.

Read the guide

Practise with the quiz: Geometry →