1. The Actual Rules for Determining the Number of Significant Figures
1. Every nonzero digit is significant (ex )
2. Sandwiched zeros are significant (ex. 404)
3. Zeros that only serve as placeholders are not significant; can’t be dropped, show magnitude (ex , , 300, 2050)
4. Zeros at the end of a number and to the right of a decimal point are significant. (ex , )
5. Exact numbers have an infinite number of significant digits. These include numbers that were counted or are defined values (ex. 40 students, 5 pencils, 100 cm = 1 m, 12 = 1 dozen)

2. Simplest Way to Determine Sig Figs EVER!!!!! (Excluding Rule 5)
If a decimal point is PRESENT, start on the PACIFIC (P) side and draw an arrow through the number until you hit a non-zero digit. Count all numbers without an arrow through them.
If a decimal is ABSENT, start on the ATLANTIC (A) side and draw an arrow through the number until you hit a non-zero digit.

3. Pacific Atlantic (dp Present) (dp Absent)
The United States
Of America g cm mL
9000 mg
70.0 kPa
0.489 L
8,000,002 mm
8,000,000 m kg