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, mm (calculator answer) The answer is expressed as or 8.3 X 10 5 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: mL mL mL = mL (calculator answer) The answer is expressed as 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.

mL mL = The first value only had three decimal places, whereas the second had four mL (correct answer) 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 mL (calculator answer)

g – 3.5 g = There is only one decimal place in the second value, whereas the first had two. 0.5 g (correct answer) 0.50 g (calculator answer) 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.

ml ml ml = There is only one decimal place in the first and second value, where as the third had two (correct answer) mL (calculator answer) 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.

g – 34.1 g = There is only one decimal place in the second value, whereas the first had three. 1.5 g (correct answer) g (calculator answer) 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.

g H 2 O g salt There are two decimal place in the first value, whereas the second had three g sol. (correct answer) g solution (calculator answer) 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.

cm cm= There is only one decimal place in the first value, whereas the second had three cm (correct answer) cm (calculator answer) 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.

mL mL = There are two decimal place in the second value, whereas the first had three mL (correct answer) mL (calculator answer) 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.

g g g = There is no decimal place g (correct answer) g (calculator answer) 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.

L + 3 L = There is no decimal place on the second value. 8 L (correct answer) 7.6 L (calculator answer) 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.

mm mm = There is no decimal place on the first value. 113 mm (correct answer) mm (calculator answer) 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.

cm X 2.5 cm = 34 cm Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors cm 2 sig. fig

cm X 2.88 cm = 900 cm Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors. 864 cm 1 sig. fig

cm _________ 90 cm 1 cm Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors. = cm 1 sig. fig

g X g = sig. fig 0.02 g Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors.

5003 mL / 3.78 mL = mL 3 sig. fig 1320 mL Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors.

3.44 kg (3.440 kg X 5 kg) kg 1 sig. fig. 0.2 kg Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors. =

m 2.30 m m 3 sig. fig. 174 m Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors. =

cm X cm = cm 2 sig. fig 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 grams. What would be the total mass, in grams of 4002 identical pieces of metal?

1.201 g X 4002 g = g 4 sig. fig 4806 g Remember: When multiplying and dividing, limit and round to the least number of significant figure in any of the factors. 4 sig. fig

20. A piece of glass is found to have a thickness of mm. What would be the total thickness of 5.0 identical pieces of glass?

0.122 mm X 5.0 = mm 2 sig. fig 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

ml m 1280 cm g kg 0.2 mm ml 3.12 L

162.2 ml 20.0 cg 3.9 dm 7.32 mm 5.8 dm L 19.8 cm