1. Rules for Significant Figures
All non zero digits are significant
1,2,3,4,5,6,7,8,9
All zeros between two non zero digits are significant
sig figs
All zeros to the right of both a number and a decimal in a decimal number are significant
sig figs

2. Significant figures
Determine the number of sig figs in each of the following measurements:
23 cm 77m
1.498g m
248.3s m
1070 g m
0.238km m
8.036m m
m m
1200m m

3. Significant figures (Answers)
Determine the number of sig figs in each of the following measurements:
23 cm 2 77m 2
1.498g m 4
248.3s m 7
1070 g m 7
0.238km m 4
8.036m m 4
m m 4
1200m m 1

4. ROUNDING NUMBERS ROUND THE FOLLOWING NUMBERS TO 2, 3 AND 4 SIG FIGS:
NUMBER 2 S.F. 3 S.F. 4 S.F.
123456
26.065

5. ROUNDING NUMBERS (ANS)
ROUND THE FOLLOWING NUMBERS TO 2, 3 AND 4 SIG FIGS:
NUMBER 2 S.F. 3 S.F. 4 S.F.

6. ROUNDING NUMBERS Round each of the following to 2 s.f. and 1 s.f.
NUMBER 2 S.F. 1 S.F.
16.97
0.173
197.67
2.52
17.99
1.0016
20.78
1.47

7. New Rule for Rounding 197.67 rounded to 2 sig figs looks like this 200
The bar over the 0 indicates a number higher than 195 and makes the 0 significant

8. ROUNDING NUMBERS (ANS)
Round each of the following to 2 s.f. and 1 s.f.
NUMBER 2 S.F. 1 S.F.

9. RULES FOR ADDING AND SUBTRACTING
Round your answer to the least precise measurement
Example
4.5 cm cm = 6.84 cm
Since your least precise measurement is 4.5 cm ( tenths), your answer will be rounded to the nearest tenth cm

10. ADDING AND SUBTRACTING WITH SIG. FIGS.
12cm cm cm=
0.085cm cm cm =
3.419g g g g =
30.5g g g g =
41.025g – 23.28g =
289kg – 43.7kg =
145.63ml – 28.9 ml =
ml – ml =

11. ADDING AND SUBTRACTING WITH SIG. FIGS. (ANSWERS)
12cm cm = cm
0.085cm cm cm = cm
3.419g g g g = g
30.5g g g g = g
41.025g – 23.28g = g
289kg – 43.7kg = kg
145.63ml – 28.9 ml = ml
ml – ml = ml

12. RULES FOR MULTIPYING AND DIVIDING
The number of significant digits in the result is the same as that of the measure of the least number of significant digits
Example
3.2 cm X cm = cm²
Since 3.2 has 2 sig figs and 2.11 has 3 sig figs
the answer has 2 sig figs
Answer: 6.8 cm²

13. MULTIPLYING AND DIVIDING WITH SIG. FIGS.
17.3cm x 6.2cm =
5.00mm x mm =
20.8cm x cm =
m ÷ 5.813m =
km ÷ 43.5 km =

14. MULTIPLYING AND DIVIDING WITH SIG. FIGS. (ANSWERS)
17.3cm x 6.2cm = cm²
5.00mm x mm = mm²
20.8cm x cm = cm²
m ÷ 5.813m =
18.82m2
km ÷ 43.5 km =
5.70km2