Significant Figures, calculations and conversion factors

Which of the following are exact numbers?

• A number you get from counting items.

• A number you get from a definition comparing units in the same measuring system

• A number you get from a definition comparing units in different measuring system.

• A number you get from using a tool to measure something

What is a measured number?

• The numbers you obtain when you measure a quantity such as your height. They must have a unit of measurement.

• An arbitrary number chosen without any criteria.
• A theoretical value that cannot be measured.
• A random number without any context.

Which of the following is a measured number?

• 5.0 m

• 5.98

• 3 apples
• 15 seconds

Answer explanation

5.98 is not a measured number because you aren't given a unit. 3 apples is an exact number because it is counting discrete items

Which of the following are exact numbers?

• 1 Kg = 2.2 lb

• 1 Kg = 1000 g

• 12 doses

• 25.5 cm

Answer explanation

Only one number in the equality 1 Kg = 2.2 lb is an exact number because they are units from different systems, the US/Imperial system and the Metric system. 25.5 cm is a measured number.

What is the rule you have to apply when multiplying and dividing measured number with different numbers of significant figures?

• The answer must use the highest number of significant figures from the measured numbers.

• Round all numbers to the nearest whole number before calculating.
• Ignore significant figures when multiplying or dividing.
• The answer use the least number of significant figures from the measured numbers.

What is the rule when adding or substracting numbers with different amount of significant figures?

• The answer must use the greatest number of decimal places from the numbers involved.

• Round all numbers to the nearest whole number before adding or subtracting.
• The answer must use the least number of decimal places from the numbers involved.

• Ignore significant figures entirely when performing the operation.

Do exact numbers affect the number of significant figures in calculations?

• Exact numbers can change the outcome of significant figures.
• Exact numbers have no significance in calculations.
• No, exact numbers do not affect the number of significant figures in calculations.
• Yes, exact numbers increase the number of significant figures.

Aiden is driving a car that travels a distance of 283.67 kilometers in 3.74 hours. Calculate the speed of the car. Express the answer using SF Rules:

Include units in your answer.

Emma is measuring the lengths of three pieces of wood for a project. The lengths are 89.4 cm, 78.56 cm, and 80.784 cm. Express the total length using SF Rules:

Include units in your answer.

What is an equality?

• An equality is a type of inequality.
• An equality is a mathematical operation.
• An equality is a statement about a single expression.
• Two numbers that use different units to describe the same quantity.