Grade 8 · Number · Rational Number Operations
Coordinate Rational Operations
A multi-step problem becomes manageable when quantities are expressed in compatible forms and each operation is interpreted before calculation.
The big idea
Represent first, calculate second
Fractions, decimals, percents, ratios, and rates can describe related quantities. The most useful representation depends on the question.
Work it through
Find the final price of an $80 item discounted 25% then taxed 13%
- 1. Find the discount: 0.25 × 80 = 20.
- 2. Subtract it: 80 − 20 = 60.
- 3. Find tax on the discounted price: 0.13 × 60 = 7.80.
- 4. Add tax: 60 + 7.80 = $67.80.