Rules on the Significant Digit problems

[louie]

I need help on these problems. Not clear on the rules, it is just two points but just tired of having those two points taken off..... Can anyone help?

[AuSmith]

A significant digit is one that is nonzero or comes after a nonzero digit.

0.00405 has 3 sig digits and
0.004050 has 4 sig digits.

For SD problems, the underlined numbers are measurements, which are rounded off. Everything else is exact (you can think of them as having as many significant digits as you wish). There are two rules for sig figs:

1) When adding two measurements, round to the same place as the less precise figure.

Ex: 2.385+0.06177=2.44677 rounded to the thousandths place (thousandths vs. hundred thousandths) = 2.447

2) When multiplying two measurements, round to the same number of sig figs as the figure with fewer sig figs.

Ex: 2.30x0.061=0.1403 rounded to 2 sig figs (3 sig figs vs. 2 sig figs) = 0.14

Sig figs are explained near the top of this page. Ask if you have questions.