In this Warm-up, students use two rulers that have different levels of precision to measure the same lines. Students notice how differences in recorded measurements can result from the level of precision of the measuring device. This prepares students for expressing measurement error as a percentage of the correct amount.
Students will need to use the rulers again later in this lesson, so make sure they keep track of them.
Arrange students in groups of 2. Distribute one set of 2 pre-cut rulers to each group.
Give students 3–5 minutes of partner work time, then follow with a whole-class discussion.
Your teacher will give you two rulers and three line segments labeled A, B, and C.
Use the centimeter ruler to measure each line segment to the nearest centimeter. Record these lengths in the first column of the table.
Use the millimeter ruler to measure each line segment to the nearest tenth of a centimeter. Record these lengths in the second column of the table.
| line segment | length (cm) as measured with the first ruler |
length (cm) as measured with the second ruler |
|---|---|---|
| A | ||
| B | ||
| C |
Sample response:
| line segment | length (cm) as measured with the first ruler |
length (cm) as measured with the second ruler |
|---|---|---|
| A | 7 | 6.7 |
| B | 7 | 6.9 |
| C | 7 | 7.3 |
Ask students to describe what they notice about the lengths they got when they used the two different measuring devices. Explain to students that one source of measurement error can be the precision level of their measuring device. Ask students, “Assuming the measurements to the nearest tenth of a centimeter are exact, how much error was in each measurement when you used the centimeter ruler?” (7 cm was 0.3 cm too long, 0.1 cm too long, and 0.3 cm too short, respectively.)
Students might not line up the edge of the ruler with the end of the line. Remind students that we need to line up the 0 mark on the ruler (in this case, the edge of the ruler) with the beginning edge of the line being measured.
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In this Warm-up, students use two rulers that have different levels of precision to measure the same lines. Students notice how differences in recorded measurements can result from the level of precision of the measuring device. This prepares students for expressing measurement error as a percentage of the correct amount.
Students will need to use the rulers again later in this lesson, so make sure they keep track of them.
Arrange students in groups of 2. Distribute one set of 2 pre-cut rulers to each group.
Give students 3–5 minutes of partner work time, then follow with a whole-class discussion.
Your teacher will give you two rulers and three line segments labeled A, B, and C.
Use the centimeter ruler to measure each line segment to the nearest centimeter. Record these lengths in the first column of the table.
Use the millimeter ruler to measure each line segment to the nearest tenth of a centimeter. Record these lengths in the second column of the table.
| line segment | length (cm) as measured with the first ruler |
length (cm) as measured with the second ruler |
|---|---|---|
| A | ||
| B | ||
| C |
Sample response:
| line segment | length (cm) as measured with the first ruler |
length (cm) as measured with the second ruler |
|---|---|---|
| A | 7 | 6.7 |
| B | 7 | 6.9 |
| C | 7 | 7.3 |
Ask students to describe what they notice about the lengths they got when they used the two different measuring devices. Explain to students that one source of measurement error can be the precision level of their measuring device. Ask students, “Assuming the measurements to the nearest tenth of a centimeter are exact, how much error was in each measurement when you used the centimeter ruler?” (7 cm was 0.3 cm too long, 0.1 cm too long, and 0.3 cm too short, respectively.)
Students might not line up the edge of the ruler with the end of the line. Remind students that we need to line up the 0 mark on the ruler (in this case, the edge of the ruler) with the beginning edge of the line being measured.