Reading Scales

Est. Class Sessions: 1–2

Developing the Lesson

Depending upon the collection you have gathered, you may wish to keep the measuring tools at stations and have student groups rotate to each to observe and discuss various scales.

Observe Scales. Distribute examples of measuring tools containing scales to groups of 2–4 students. Ask students to take a couple of minutes to examine the scale on their tool, discuss what they observe with their group, and then pass along their tool to another group. Repeat until each group has looked at 3 to 4 different kinds of scales.

When observation is complete, launch a discussion of the word scale: a series of spaces marked by lines, dots, or numbers that is used for measuring quantities.

Display several examples of tools examined, and ask:

All of these objects are tools used for measuring. How are all of these tools alike? (Possible response: They all have lines or dots and numbers on them.)
What do you notice about the numbers on these tools? (Possible responses: There is skip counting on them to count by fives, tens, twenties, etc. They all have zeros on them.)
The lines and numbers or dots are called a scale. The scale is used to read a measurement. What could you measure using the tools we looked at today? (Answers will vary.)
What are some other examples of scales you have seen? Where did you see them? (Possible responses: on the dashboard of the car, on a grocery store scale, on my bathroom scale, on a barometer at home, on a bar graph we made in class)

Using your examples of scales, explain that scales have different units of measurement and measure different aspects of the world. Use displays of the Thermometer, Speedometer, and Graduated Cylinder Masters to discuss the units of measurement on each. Discuss how each unit would be labeled when written.

While displaying the Graduated Cylinder Master, direct students' attention to the unit of measurement, milliliters (ml). A milliliter is equivalent to a cubic centimeter (cc). Graduated cylinders are generally marked with milliliters, but the cubic centimeter is the metric unit of volume we will use. See Content Note.

We prefer the term cubic centimeter (cc) because it reminds students of the meaning of the unit—a cube that is 1 cm on each side or a cubic centimeter. The terms milliliter and cubic centimeter may be used interchangeably.

Sometimes a scale is called by another name such as a dial or a meter.

Create Tools with Scales Chart. Have students help you fill in the tools with scales chart you prepared prior to the lesson. See Materials Preparation. Your chart may vary depending on the scales you have for examples and the suggestions your students make. See Figure 2.

Read Scales on Graduated Cylinders. Using displays of the Scale 1 with Blowup, Scale 2 with Blowup, and Scale 3 with Blowup Masters, ask students how they would use the scale to show various quantities on each of the graduated cylinders represented. Have volunteers touch the lines on each scale on the displays and skip count by twos, fives, and tens to determine what numbers go with lines that are not numbered. Display the Scale 1 with Blowup Master.

Ask prompts similar to the following:

Think of the tools you saw with your group. This is part of a scale on one of them. What tool uses a scale like this? (a graduated cylinder)
What is the unit of measure and label for this graduated cylinder? (cubic centimeters or cc)
How do you know if you should count by twos, fives, or tens on each kind of scale? (Possible response: Look at the bottom of the scale to see how many marks are between zero and the next number. Then you can tell if it counts by ones, twos, fives, or tens.)
How are measurements represented on Scale 1? (Possible response: The numbers skip count by 10s. When I counted starting at 0 and go to 10 there is a line for each number. That means each line is 1 cc and the medium-sized line in the middle shows 5 cc; five is halfway between 0 and 10.)

Point to or draw a heavy line on the mark showing 25 on the enlarged scale.

Ask:

If this cylinder is filled with water to this mark, how much water is in the cylinder? Remember to use a label in your response. (25 cc)
How do you know? (It is halfway between 20 and 30. The middle line shows 5 more than the number before it, which is 20, so that means the measurement is 25 cc.)
Show us how you can skip count on this scale to find this measurement. Point to the marks as you count. (Pointing to the appropriate marks: 0, 5, 10, 15, 20, 25)
Who can show us how to find 32 cc? Point to each mark as you count. (pointing to the appropriate marks: 0, 5, 10, 15, 20, 25, 30, 31, 32)

Continue pointing to specific lines on the different scales and ask students to tell the numbers that go with those lines. Give students numbers and have them skip count and point to the corresponding lines on the scale. Include amounts that may lie between lines, for example, finding 13 cc on the Scale 2 with Blowup Master. Use similar prompts with the remaining two Masters. Help students realize the differences on each:

The Scale 2 with Blowup Master depicts one line for every two cubic centimeters, and multiples of 10 cc are labeled; half, or 5 cubic centimeters would be half way between the lines showing 4 and 6 cubic centimeters.
The Scale 3 with Blowup Master depicts one line for every two cubic centimeters and multiples of 20 cc labeled. On this scale, discuss that the halfway mark represents a ten. Also note that another difference is that Scale 3 goes beyond 210 cc.

Assign the Scales pages from the Student Activity Book to student pairs. Encourage them to examine each scale to note how each is alike or different before starting. Remind them to label their answers. As students work, circulate to observe how they are reading each scale and guide students as needed.

After student pairs complete the pages, use display pages to discuss students' responses to questions. Have students demonstrate how they counted and used each scale to determine answers.

Ask prompts similar to the following:

How are these two scales alike? (Possible responses: They both begin at zero. They are both vertical/up-and-down scales. They both skip numbers.)
How are they different? (Possible responses: The scale in Question 1 depicts one line for every cubic centimeter and multiples of 10 cc are labeled; the scale in Question 2 depicts a scale with one line for every 2 cubic centimeters and only even multiples of ten are labeled.)
Who can show us how you found the answer to [Question 1E]?

Read Other Scales. Use displays of the Thermometer and Speedometer Masters to practice reading additional scales.

Ask:

How is this scale like those on the graduated cylinders? How is it different?
What do you think this scale measures? Where do you see it?
What is the unit of measurement on this scale?
Does this scale count by ones, twos, fives, or some other amount?

Point to specific lines on each scale and ask students to tell the measurements that go with those lines. While viewing the Thermometer Master, point out and discuss the unit of measurement and the label used to represent degrees Fahrenheit. While discussing the Speedometer Master, define the term and explain that the unit of measurement, mph, is an abbreviation for miles per hour.

Have students complete the Thermometers and Speedometers pages in the Student Activity Book. Remind students to label their measurements. When adequate time has been provided, have students discuss and explain how they determined measurements.

Ask:

How did you find 103° on the thermometer? (Possible response: I found 100 and went up 3 lines because each line is one degree.)
What do you notice about the numbers on the thermometers? (They skip count by tens, but there is a 10 and 20 below the zero with a minus sign before each.)
Why do you think there are minus numbers? What do you think that means? (Possible response: I heard the weatherman on the news in the wintertime say the temperature was below zero. That was really cold! Maybe it's for when it's really cold outside, like on a number line there's zero, but this is less than that.)
How did you find 55 mph on the speedometer? (Possible response: I looked between 50 and 60 and know it's the line half way between like on a number line.)
In Question 5A Tara thinks the speedometer read 81 mph. Do you agree? Why or why not? (Possible response: The speedometer is counting by fives and the arrow is halfway between 80 and 90 on the 85 mark. 81 mph would be just a little bit past the 80 but there is no line to show exactly 81 mph.)