Proportion equations · Grade 9
In Grade 9 you learn: inverse proportion equations.
When two quantities are in proportion, you can write a formula linking them, find the constant k from one pair of values, and then use the formula for any other value. Many science laws — springs, gravity, light — are proportion formulas.
Key facts
- Method: write the formula with k. Put in the pair you know to find k. Then use the formula.
- Direct: y ÷ x stays the same (straight-line graph through the origin). Inverse: x × y stays the same.