How do I express a decimal in scientific notation? I know how to do it with whole numbers, but don't know what the rules are when the number is something like .00075.

Answer 1

the decimal is always placed after the first signigicant digit, in your case 7.5, then count the number of decimal places it was moved. That becomes your exponent of 10
if you had to move to the right, the exponent is negative, if you moved to the left, the exponent is positive.
so .0075 = 7.5 x 10^-4

34567.21 = 3.456721 x 10⁴