Question 777394
When multiplying, the result is only as accurate as the term with the least amount of significant figures.


642 => 3 sig figs
4 => 1 sig fig
10^(-5) => 5 sig figs


642 * 4 * 10^(-5) = 0.02568 = 0.03


Here is some more information about significant figures:


https://www.nku.edu/~intsci/sci110/worksheets/rules_for_significant_figures.html