Ratios, rates, percentage change and direct versus indirect variation

What this note covers

1. Three ways of comparing quantities, and how to tell them apart
2. Ratios: simplifying, dividing a quantity, and the part-to-whole trap
3. Rates, unit pricing and the better buy
4. Percentage change: increase, decrease, mark-up and discount
5. Reverse percentages: finding the original amount
6. Direct variation: when doubling one doubles the other
7. Indirect variation: when doubling one halves the other
8. How ratio and percentage work is marked, and where the top band is won

8 sections · 12 key terms & formulas · 6 common mistakes