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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) A P 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. 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