# Exponential growth and decay by percentage

### Exponential growth and decay by percentage

Exponential growth/decay rates can be presented in percentages. We will work on questions of this kind in this lesson.

Exponential growth/decay rates can be presented in percentages. We will work on questions of this kind in this lesson.

${A_f}$: final amount

${A_i}$: initial amount

${f }$ : growth/decay factor

half-time$\to f = {1\over 2}$

triple$\to f = {3}$

ten-fold$\to f = {10}$

increase by 10%$\to f = {({1 + {10\over 100}}) } { = 1.1}$

decrease by 8%$\to f = {({1 - {8\over 100}}) } { = 0.92}$

${time}$ : total time given

${period}$ : every length of time