1. Significant Figures “Sig Figs”
Atlantic-Pacific Rule

2. Atlantic-Pacific Rule
Decimal Present – Pacific
Decimal Absent – Atlantic
Ex g
Sig Figs
Start on the Pacific (left side) with the 1st non-zero & count to the end
Ex g
Sig Figs
Start on the Atlantic (right side) with the 1st non-zero & count to the end
Pacific
Atlantic

3. Examples: Counting Sig Figs
520 mL
decimal absent start from the Atlantic (right side) with the 1st non-zero and count to the end
2 Sig figs ms
decimal present start from the Pacific (left side) with the 1st non-zero and count to the end
3 sig figs
0.230 kg —3 sig figs
L —3 sig figs

4. Rules for Adding/Subtracting with Sig Figs
The answer to an addition or subtraction problem must have the same number of decimal places as the measurement with the least number of decimal places.
Examples:
1.3453g + 3.2g (the measurement with the least # of decimal places is 3.2g. It has 1 decimal place, so the answer must have just 1 decimal place)
Answer: 4.5 g
5.73mL – mL (5.73 has 2 decimal places)
Answer: -0.62mL (our answer needs 2 decimal places)
3.333s s + 1.1s
Answer: 6.7 s

5. Multiplying/Dividing with Sig Figs
The answer to an multiplication or division problem must have the same number of Sig Figs as the measurement with the least number of Sig Figs.
Examples:
g x 45.2 g (45.2 has the least number of sig figs—it has 3 sig figs. So, our answer needs 3 sig figs.
Answer: 14.9 g
0.258 mL ÷ mL (0.258 has the least # of sig figs—it has 3. So, our answer needs 3 sig figs)
Answer: mL