and when we multiply 1000.00 * 0.05 = 10500.00

can someone explain how is that happen? I'm weak in algebra so I want to understand this scientifically not just add numbers and multiply

because I know how to multiply and add numbers but I don't know the explanation of that and the scientific reasons

please explain that for me because I'm about to be a lecturer in the future I want to ask all the questions that giving to me

please