Answer:
We'd like to take a repeating decimal and express it as a quotient of two whole numbers. The idea is to multiply by some number (10, 100, 1000, etc.) so that when we subtract the original number from the multiple, the repeating part cancels out. If we multiply by 10, we get 10x = 2.
Explanation:
1.28 = 128 * 10^-2
128 * (1/10^2)
128 / 10^2
128 / 100
= 1.28
Because, it's literally the same thing mathematically if you worked it out. Though, as I'm sure you're aware, it's just a much shorter and cleaner way of writing out large or small numbers.