Question

What do exponential growth and decay have in common?

Answer 1

They both work with the same equation: `N=B*g^t`
Where
`N=` new situation
`B=` begin
`g=` growth factor
`t=` time

If the growth-factor is greater than `1`, then we have a growth.
If it is less than `1` we call it decay.
(if `g=1` nothing happens, a stable situation)

Examples:
(1) A population of squirrels, starting at 100, grows by 10% every year. Then `g=1.10` and the equation becomes: `N=100*1.10^t` with `t` in years.
(2) A radio-active material with original activity of 100, decays by 10% per day. Then `g=0.90` (because after a day only 90% will be left) and the equation will be: `N=100*0.90^t` with `t` in days.