Thank you! May be I didn't present the question clearly enough. The point of the question is: Is there a reasoned method to decide how may significant digits to show when one is asked to convert a number from its decimal representation to scientific notation WITHOUT being given any further...
This question has to do with some annoying anomaly when expressing in scientific notation whole numbers that are multiples of powers of 10. For instance, 2000 is usually written in scientific notation as 2x10^3, implying that the original number has 1 significant digit. On the other hand, 2025...