eli5: Why does there need to be 11 additional dimensions for the string theory to work?

Question

eli5: Why does there need to be 11 additional dimensions for the string theory to work?

In: 5

Answer 1

Because the math works out if you put existing data into a higher dimension space.

There is no standard way to interpret why it worked, but if the math works, the interpretation coming after it works as a theory.