Percent Increase
When a quantity grows (gets bigger), then we can compute its PERCENT INCREASE: |
Visualizing Percent Increase
NOTE:
If $\,\text{percent increase} = 75\%\,$, then the formula $$\text{percent increase} = \frac{\displaystyle{(\text{new} - \text{original})}} {\displaystyle\text{original}} $$ becomes $$75\% = \frac{\displaystyle{(\text{new} - \text{original})}} {\displaystyle\text{original}} $$ and solving for ‘new’ gives: $$ \text{new} = \text{original} + 75\%(\text{original}) $$ |
Percent Decrease
When a quantity shrinks (gets smaller), then we can compute its PERCENT DECREASE:
Both formulas have the following pattern:
Note that when you compute percent increase or decrease, Note also that the numerator in these formulas is always a POSITIVE number |
Visualizing Percent Decrease
NOTE:
If $\,\text{percent decrease} = 25\%\,$, then the formula $$\text{percent decrease} = \frac{\displaystyle{(\text{original} - \text{new})}} {\displaystyle\text{original}} $$ becomes $$25\% = \frac{\displaystyle{(\text{original} - \text{new})}} {\displaystyle\text{original}} $$ and solving for ‘new’ gives: $$ \text{new} = \text{original} - 25\%(\text{original}) $$ |