These can then easily be multiplied and divided using the rules above. The exponents of e are called natural logarithms. It is the value reached in a unit time by a unit quantity that grows at a rate equal to itself. After a short time the dollar will have gained value. One natural system that appears to show exponential growth is population.
Exponential decay is simply a quantity that decreases at a rate equal to itself.
This behavior is shown by radioactive decay. The fewer the atoms the more slowly the number decreases. The minus sign shows the number will get smaller.