Significant Figures“Sig Figs”

Atlantic-Pacific Rule

Atlantic-Pacific Rule

PacificAtlantic

Decimal Present – Pacific

Decimal Absent – Atlantic

Start on the Pacific (left side) with the 1st non-zero & count to the end

Ex. 1.250 g1 2 3 4 4 Sig Figs

Ex. 12500 gStart on the Atlantic (right side) with the 1st non-zero & count to the end

3 2 1 3 Sig Figs

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

• 0.0102 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• 25 600 L —3 sig figs

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 – 6.3456mL (5.73 has 2 decimal places)– Answer: -0.62mL (our answer needs 2

decimal places)• 3.333s + 2.22s + 1.1s– Answer: 6.7 s

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:• 0.3287 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 ÷ 0.36105 mL (0.258 has the least # of sig figs—it has 3. So, our answer needs 3 sig figs)–Answer: 0.715 mL