How many significant figures are found in the value 5.5550x10?

Answer 1

Trailing zeros after a decimal point should be significant digits; otherwise, there would be no reason to write them. By this rule, the given number has five significant digits.

Additional answer

It is incorrect to put trailing zeros after the decimal digits because they have no meaning. Therefore there are four significant figures both before and after the multiplication by 10. That multiplication merely shifts the decimal point one place to the right without altering the number of significant figures.

• Please the following except from Wikipedia: Trailing zeros in a number containing a decimal point are significant. For example, 12.2300 has six significant figures: 1, 2, 2, 3, 0 and 0. The number 0.000122300 still has only six significant figures (the zeros before the 1 are not significant). In addition, 120.00 has five significant figures since it has three trailing zeros. This convention clarifies the precision of such numbers; for example, if a measurement precise to four decimal places (0.0001) is given as 12.23 then it might be understood that only two decimal places of precision are available. Stating the result as 12.2300 makes clear that it is precise to four decimal places (in this case, six significant figures).