How many significant figures are in the number 4.270000?

Answer 1

As trailing zeros after a decimal point are not normally written, for them to be written means they must have significance, so 4.270000 has 7 significant figures (it may have been rounded from 4.2699995 to 7 sig fig).

4.27 (the same value) would only have 3 sig fig.

Answer 2

Here are 7 significant figures.