The Actual Rules for Determining the Number of Significant Figures 1. Every nonzero digit is significant (ex. 2317.9) 2. Sandwiched zeros are significant (ex. 404) 3. Zeros that only serve as placeholders are not significant; can’t be dropped, show magnitude (ex. 0.0047, 0.0000000000000003, 300, 2050) 4. Zeros at the end of a number and to the right of a decimal point are significant. (ex. 47.30, 3.0000) 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)

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.

Pacific Atlantic (dp Present) (dp Absent) The United States Of America 0.00235 g 0.0700 cm 100.23 mL 9000 mg 70.0 kPa 0.489 L 8,000,002 mm 8,000,000 m 0.0000000001 kg