How many significant figures does the number 1000.00 contain?

Answer 1

1000.00 has four significant digits. Basically the total amount of significant digits will be the amount of numbers it needs to retain the same value.

I.e. 126.26 has 5 significant digits, because you need all 5 to make the same value.

120.00 has three significant digits, because .00 if removed would not change the value of the number.

Answer 2

6 of them.