Brainlag PlusPopulations, bacteria, half-lives and iteration formulas: exponential models, and finding a growth rate from two values.
Multiply by the same number each time
Growth by 4% a year: × 1.04 each year.
Doubling every 20 minutes: × 2 for each 20 minutes, so in 2 hours × 2⁶ = × 64.
A half-life of 6 hours: after 18 hours, three halvings: × (1/2)³ = ÷ 8.
An iteration formula says the same thing step by step: Pₙ₊₁ = 1.04Pₙ.
The rest of this lesson and its 7 practice questions are in Plus.
Screen 1 of 3, free to read.
- 7 exam-style questions, marked as you go, each with a worked solution
- The Graphing Calculator beside every question
- Anything you get wrong is saved to your flashcards