All SAT GuidesStudy Guide
Exponential Functions
Exponential change multiplies by the same factor during equal time intervals. Growth by r as a decimal uses factor 1 + r; decay uses factor 1 − r.
Key Rules
- Write a model as initial amount times factor raised to the number of intervals.
- Convert a percent change to a decimal before finding the factor.
- Match the exponent to the stated time unit.
Common Mistakes to Avoid
- Adding a fixed amount when the problem describes a fixed percentage.
- Using 0.25 as the growth factor for a 25% increase instead of 1.25.
SAT Strategy Tips
- →Calculate one interval to check whether the amount should grow or shrink.
- →At zero intervals, the model must return the initial amount.
Example Question
An initial population of 80 increases by 25% each year. What is the modeled population after 2 years?