Worked examples
Two examples
Example 1
Which unit is the best one for measuring the length of a pencil: millimeters, centimeters, meters, or kilometers?
- First ask what is being measured. A pencil’s length is a length, so the unit must be a unit of length. All four choices are.
- Then picture each one. A millimeter is about the thickness of a coin. A centimeter is about the width of a fingernail. A meter is about the height of a kitchen counter. A kilometer is about a ten-minute walk.
- A pencil is about 18 fingernail-widths long: about 18 centimeters. That is a number easy to picture and to work with.
- In millimeters it would be 180, which is not wrong, but larger than it needs to be. In meters it would be 0.18, and in kilometers 0.00018.
Answer: Centimeters
Example 2
Which is a sensible measurement of the mass of an apple: 150 milligrams, 150 grams, or 150 kilograms?
- Mass is how much matter something has. It is measured in milligrams, grams and kilograms.
- A paper clip has a mass of about 1 gram. A bag of sugar is about 2 kilograms.
- 150 kilograms is heavier than two grown people. 150 milligrams is about as light as a few grains of rice.
- An apple is about as heavy as 150 paper clips: 150 grams.
Answer: 150 grams
Where this is taught: Science Practices, part 6: Numbers and units in science · Look Again Quiz 6: Numbers in Science
In your Kaplan book: Unit 4, Chapter 1, Lesson 6: Apply Scientific Formulas · Map of the Terrain, topic 6: Numbers in science
The drill
Ten questions
How many:
Read what is in the box first, if there is one. Then tap your answer; a few questions ask you to choose words from a drop-down instead, the way the GED test does. Press Check my answers at the bottom.Read what is in the box first, if there is one. Circle your answer; where there are brackets, circle the choice that fits. The answer key, with the reasoning, is on the last page.