Estimating Metric Length

Unit of Study 9: Length in MetricGlobal Concept Guide: 2 of 3

Content Development

By using the direct comparison strategy, students become better at making reasonable estimates.

When students are asked to select the best unit for measuring they need to connect the inverse relationship between the size of the unit and the number of units used to measure the length. The smaller the unit the more of the unit you will need to measure. For example when asked to measure the distance from home to school the number of

meters would be much less than the number of centimeters. They could both be used but meters would be the more practical choice.

Learn Zillion video ~ Quick code 3658 - Understand EstimationQuick code 3659 - Decide if an Estimate is ReasonableQuick code 3660 - Estimate Length by Creating a Mental Ruler

Day 1 Essential Question: How do you use known lengths to estimate unknown lengths? The focus of this day is for students to gain a better understanding of how to use known lengths

(referent) to estimate the length of an unknown using the centimeter unit. The following could be a possible engagement on Day 1:

Facilitate a discussion about the estimates students made. Some questions could include: How do you know your estimate is reasonable? What would you do to check your measurement?

Then, distribute a ten rod, which is approximately 10 cm long to each student. Students will use this referent or “known” length to estimate lengths of unknowns objects. Focus on the vocabulary: shorter than, longer than, the same as etc.

Students can practice using the referent or “known” length to estimate various objects in your classroom and record them on the Estimate length in centimeters chart. Students should estimate the length and then measure to confirm if their measurement was reasonable or not. Note: you may need to change the listed objects to fit your classroom.

Day 1 continued

To continue applying estimation, students can complete the following task:

Elements of GO Math Lesson 9.2 can be used on Day 1 to help students grasp the concept.

Students can also apply their understanding in Estimating Lengths By the end of Day 1, students will be able to use a referent (“known” length) to

estimate unknown lengths of objects.

Day 2 Essential Question: How do you estimate the lengths of objects in meters? The focus of day 2 is estimating the length of objects in meters. Students should

be encouraged to use objects they know are about 1 meter long (baseball bat) to estimate the lengths of unknown objects.

Possible Engage: Students can start to build understanding of the size of a meter by completing the following:

Extend the activity and have students stand farther apart and estimate the distance between them in meters. Have students justify why they estimated the various distances. Circulate to ensure the estimates are reasonable. We want students to build a strong understanding of the size of a meter.

Day 2 continued Elements from Go Math Lesson 9.6 can be used to have students estimate

objects in meters. Utilize, Estimate length in meters chart to guide students in estimating

lengths in meters. After estimating, students should conduct actual measurements to confirm if their estimates were accurate/reasonable or not. Note: you may need to change the listed objects to fit your classroom.

By the end of Day 2, students will be able to make reasonable estimates about lengths of objects in meters.

Sample conversation

Day 3 Essential Question: How do you know if you should estimate length using

centimeters or meters? The focus of this day is for students to estimate lengths in centimeters and

meters. Students will need to determine which unit of measurement is most appropriate to use when estimating.

Students will need to have discussions justifying their reasoning for choosing meters of centimeters.

The students should be exposed to both real world measurements as well as paper and pencil examples.

An excellent task to have students practice this skill is:

Day 3 continued Students need authentic opportunities to measure objects and determine

which unit would be the most appropriate for making reasonable estimates.

Another option is the following lesson from CPALMS:

Measuring Madness- focus on the sections where students use metric measurement (centimeters and meters).

By the end of Day 3, students will be able to select the appropriate unit when using metric measurement.

Enrich/Reteach/Intervention

Reteach: Reteach p. R87 Reteach p. R91 For students who are struggling, continue to provide support

with using referents and have them make comparisons.

Enrich Enrich TE p 437B,Enrich page E87Enrich page E91Challenge students to draw 3 line segments (without

a ruler) that total approximately 20 centimeters. The number of lines and total centimeters or meters can vary to extend the activity.