How many significant figures are there in 0.08240?

Answer 1

As trailing zeros after a decimal point make no difference to the value of a number and are not normally written but 0.08240 does have one written, the trailing zero must be significant. Counting form the first non-zero digit to the last significant digit (inclusive) there are 4 sig fig.

Answer 2

There are 4. The last zero is significant because if it were not, it would not appear.