Rule 1: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
Example 1:
39.0 mm X 385 mm X 55 mm =
825,825.00 mm (calculator answer)
The answer is expressed as
830 000 or 8.3 X 105 since 55 mm has two
significant figures.
Rule 2: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
Example 2:
643.40 mL + 40.0 mL + 55.001 mL =
738.40 mL (calculator answer)
The answer is expressed as 738.4 mL since
40.0 mL has only one decimal place.
Carry out the following calculations
expressing your answers to the
correct number of significant figures.
Assume that all numbers are
measured quantities.
1. 0.742mL + 0.0259mL = 0.7679mL
(calculator answer)
0.768mL (correct answer)
The first value only had three
decimal places, whereas the
second had four.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
2. 4.00 g – 3.5 g = 0.50 g
(calculator answer)
0.5 g (correct answer)
There is only one decimal place
in the second value, whereas the
first had two.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
3. 22.1 ml + 33.2 ml + 224.08 ml
= 279.38 mL
279.4 (correct answer)
(calculator answer)
There is only one decimal place
in the first and second value,
where as the third had two.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
4. 35.601 g – 34.1 g = 1.501 g
(calculator answer)
1.5 g (correct answer)
There is only one decimal place
in the second value, whereas the
first had three.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
5. 150.00 g H2O
+ 0.507 g salt
150.507 g
solution
(calculator answer)
150.51 g sol. (correct
answer)
There are two decimal place in the
first value, whereas the second had
three.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
6. 67.5 cm - 0.009 cm= 67.491 cm
(calculator answer)
67.5 cm (correct answer)
There is only one decimal place
in the first value, whereas the
second had three.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
7. 0.008 mL + 0.05 mL = 0.058 mL
(calculator answer)
0.06 mL
(correct answer)
There are two decimal place in
the second value, whereas the
first had three.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
8. 250.001 g + 2.000 g + 5000.00 g =
5252.001 g
(calculator answer)
5252.00 g (correct answer)
There is no decimal place
250001.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
9. 4.60 L + 3 L =
7.6 L
(calculator answer)
8 L (correct answer)
There is no decimal place on the
second value.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
10. 200 mm - 87.3 mm = 112.7 mm
(calculator answer)
113 mm (correct answer)
There is no decimal place on the
first value.
Remember: When adding and subtracting,
limit and round your answer to the least
number of decimal places in any of the
numbers that make up your answer.
11. 13.7 cm X 2.5 cm = 34.25 cm
34 cm
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
12. 300 cm X 2.88 cm = 864 cm
900 cm
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
13.
89 cm
_________ = 0.988888889 cm
1 sig. fig
90 cm
1 cm
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
14.
0.00003 g X 727.0 g = 0.02181
0.02 g
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
15.
5003 mL / 3.78 mL = 1323.544974 mL
1320 mL
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
16.
3.44 kg
= 0.2 kg
(3.440 kg X 5 kg)
0.2 kg
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
17.
400.00 m
2.30 m
=
173.9130435 m
174 m
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
18.
350.00 cm X 0.00072 cm = 0.252 cm
0.25 cm
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
19. A piece of metal is found to have a mass of
1.201 grams. What would be the total mass,
in grams of 4002 identical pieces of metal?
19.
1.201 g X 4002 g = 4806.402 g
4806 g
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
20. A piece of glass is found to have a thickness
of 0.122 mm. What would be the total
thickness of 5.0 identical pieces of glass?
20.
0.122 mm X 5.0 = 0.61 mm
0.61 mm
Remember: When multiplying and dividing,
limit and round to the least number of
significant figure in any of the factors.
Significant Figures
Page 21 Answers
0.0299 ml
140 000 m
1280 cm
0.988 g
2475.0 kg
0.2 mm
23480 ml
3.12 L
162.2 ml
20.0 cg
3.9 dm
7.32 mm
5.8 dm
0.899 L
19.8 cm