Ways to compare two quantities
- Difference
- Ratio
requirements: same unit.
ratio does not give the actual number. “relative”
part-part or part-whole model
- 2:7 or 2/7 if part-part: means for every 7 Thing I, there are 2 Thing II.
- 2:9 or 2/9 if part-whole: out of each 9 Things, there are 2 Thing I.
use ratios to find how many times one number or quantity is as great as another.
Equivalent ratios and simplest forms
regroup by same factors shared by both quantities.
common divisor – division
On the opposite, we can find equivalent ratios by multiplication.
Proportionally expand or shrink
Find the missing term of a pair of equivalent ratios
4:5 = 12:?