Maths shortcuts

Any percentage of any number, in your head.

• Any percentage, starting from 10%Find 10% by moving the decimal, then build everything else from it.
• Swap the percentage round18% of 50 is hard. 50% of 18 is easy. They are the same answer.
• Fractions to percentages on sightLearn eight fractions and you can convert almost anything.

Square numbers instantly when they follow a pattern.

• Square any number ending in 5Multiply the front by the next number, then stick 25 on the end.

Interest, profit and loss the way exams ask for them.

• Averages without adding everythingPick a middle number and only average the small differences.
• Simple interest in one linePrincipal times rate times time, all over a hundred.
• Profit and loss percentageAlways divide by the cost price — never by the selling price.