Unit 4 Lesson 8

Counting by Weighing

Weighing really lightweight objects to help find the mass is a lot more difficult and less accurate than when weighing heavier objects. To accurately weigh one you must:

• Weigh a group of the identical objects
• Divide that weight by the number of objects
• Gives an average weight for one

Knowing the average weight of one object means you can pretty accurately determine the number of the objects in a large group by weighing the larger group and dividing that by the average weight.

Percent Error

Percent error allows you to see how close your answer is to the actual answer.

Formula: |(observed value - actual value)| • 100

actual value

 Practice Problems
4) the rice because rice is generally smaller than beans so more of them would be needed to equal 50 grams of beans.
5) 740 marbles has more mass because they are bigger and so take up more mass

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