What are the rules in changing exponential number to common number?

Answer 1

For a positive exponent, move the decimal point to the right, as many digits as indicated by the exponent. Fill out with zeroes as needed. Example: 5.3 x 103 = 5300 (there is an implicit decimal point at the end; you can write it explicitly as 5300.0).

For a negative exponent, move the decimal point to the left. Again, fill out with zeroes as needed. Example. 2.3 x 10-6 = 0.0000023