ELI5: Explain Like I'm 5

Esenin-Volpin's theorem

Okay, so imagine you have a really big number line. Like the one your teacher uses in math class. This number line has all the numbers in the world on it, from the smallest number you can think of to the biggest number you can think of.

Now, let's say you want to find a number on this number line that is a perfect square. A perfect square is a number that you get when you multiply a number by itself. For example, 4 is a perfect square because 2 x 2 = 4.

But here's the thing: there are an infinite number of numbers on this number line, so it might seem like it's going to be really hard to find a perfect square.

That's where Esenin-Volpin's theorem comes in. It says that if you take any number on the number line and divide it by its square root, you will get a number that is very close to the square root. And if you keep doing this with the new number you get, you will eventually get a number that is exactly the square root.

So let's say we pick the number 100. The square root of 100 is 10. If we divide 100 by 10, we get 10. If we do the same thing with 10, we get 10 again. And if we keep doing this over and over again, we will eventually get exactly 10.

So, this theorem makes it easier for us to find perfect squares on the number line, because we can use it to get really close to the square root of any number. And once we're close enough, it's much easier to just figure out the exact square root.