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Parts per Hundred
Parts per Hundred
Sales, discounts, tax, interest rates, exam scores - percentages are everywhere! They let us compare things fairly: is 17 out of 20 better than 42 out of 50? Convert both to percentages (85% vs 84%) and it's clear. Percentages are the universal language of proportions.
What is a percentage?: Parts per hundred
Percent = per cent = per 100
% symbol means 'out of 100'
50% = 50/100 = half
Mathematics glossary
- What is a percentage?
- Parts per hundred Percent = per cent = per 100 % symbol means 'out of 100' 50% = 50/100 = half
Earn the mark scheme marks
Common Mistakes to Avoid
❌ Wrong: 30% of 80 = 30 × 80 = 2400
✅ Right: 30% of 80 = 0.3 × 80 = 24
Convert percentage to decimal first
❌ Wrong: 20% increase = × 0.2
✅ Right: 20% increase = × 1.2
Add to 100% for increase (120% = 1.2)
❌ Wrong: 15% decrease = × 1.15
✅ Right: 15% decrease = × 0.85
Subtract from 100% for decrease (85% = 0.85)
Now try it yourself
Quiz · Question 1 of 14
Which calculation correctly finds 35% of £240 using the decimal method?
Tap an answer to check it