The last number is a unit. 5. The fifth power of 10 multiplied by10 is 5. 10/0000. Since 5. 10 is a valid number, 5. 10 is accurate to 0. According to the fact that the reduced 0 is exactly a thousand, it is accurate to a thousand. 2000 itself is a valid number, so it is accurate to one place. What we say is accurate to the last significant figure!