What are the practical uses of e ?

How can e be used for practical mathematics? This is for a presentation on (among other numbers) e, aimed at people between the ages of 10 and 15.

To clarify what I want:

Not wanted: ${e}^{i\pi}+1=0$ is cool, but (as far as I know) it can't be used for practical applications outside a classroom.

What I do want: e I think is used in calculations regarding compound interest. I'd like a simple explanation of how it is used (or links to simple explanations), and more examples like this.

How can e be used for practical mathematics? This is for a presentation on (among other numbers) e, aimed at people between the ages of 10 and 15.

To clarify what I want:

Not wanted: ${e}^{i\pi}+1=0$ is cool, but (as far as I know) it can't be used for practical applications outside a classroom.

What I do want: e I think is used in calculations regarding compound interest. I'd like a simple explanation of how it is used (or links to simple explanations), and more examples like this.