How many eight digit numbers are there?

Answer 1

There are 90,000,000 whole numbers.

If you include negative numbers, this doubles to 180,000,000.

If you include decimal numbers, eg 1.2345678, there are 666,000,000 positive numbers, disallowing numbers with extraneous 0's.

Including negative numbers, this doubles to 1,332,000,000

If you allow trailing 0's in the decimal place, than this becomes 730,000,000 non-negative numbers, or 1,459,999,999 numbers (since -0.0000000 = 0.0000000)

If you allow a decimal point without a digit in front, there are a further 90,000,000 non-negative numbers, or 180,000,000 including negative numbers.

Allowing trailing 0's, this becomes 100,000,000 non-negative or 199,999,999 numbers.

Maximum total:

1,659,999,998 allowing trailing 0's, and allowing numbers without a digit in front of the decimal point.