ELI5: Explain Like I'm 5

Euler number

Euler's number, also known as "e," is a special number that mathematicians use to solve problems involving growth or change over time.

Imagine you have a magical bank account that gives you more and more money as time goes on. The amount of money you have in the account at any given time depends on how long you've had the account and how much you initially put in. This magical bank account has a special property: the more often you calculate the balance, the more accurate your estimate will be.

Now, let's imagine that instead of a magical bank account, we have a regular bank account that gives you interest on your money. The interest rate is fixed, which means it doesn't change over time. If you deposit $100 into the account, and the interest rate is 10% per year, after one year, you will have $110 ($100 + 10% of $100). After another year, you will have $121 ($110 + 10% of $110).

But what if the interest is not given every year, but instead every month, every day, or even every instant? How much money will you have after a certain amount of time? This is where Euler's number comes in!

Euler's number can help us solve this problem by giving us the answer if we calculate the interest continuously, instead of at specific intervals. In simpler terms, it means we get to calculate the interest all the time, without waiting for a specific day or month to pass.

To calculate the balance of our bank account using Euler's number, we use a special formula: the balance equals the initial amount of money multiplied by Euler's number, raised to the power of the interest rate, multiplied by the amount of time that has passed.

For example, imagine we deposit $100 into an account with an interest rate of 100% per year, and we want to calculate the balance after 1 year. Using Euler's number (which is approximately 2.718), we can plug the values into the formula:

Balance = $100 * 2.718^(1 * 1)

When we calculate this, we find that the balance after one year will be approximately $271.82.

Isn't that amazing? Euler's number helps us calculate the growth of our bank account when the interest is given continuously, instead of waiting for specific intervals. Mathematicians use this number in many different areas, such as population growth, compound interest, and even in physics and engineering. It is a very useful tool that helps us understand how things change and grow over time.
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