# What Is Your Best-imate? (Making 'Best Estimates')

Subjects

Mathematics
--Applied Math
--Arithmetic
--Measurement
--Statistics

3-5
6-8
9-12

Brief Description

Estimate the number of kernels on an ear of corn. Plus more estimating challenges!

Objectives

Students will

• understand the difference between a guess and an estimate.
• make reasonable estimates for a variety of scenarios provided.

Keywords

guess, estimate, estimation, corn

Materials Needed

• an ear of corn for each group of students, plus one ear for the teacher (try to purchase ears of corn that are similar in size)
• a chart for students to fill in (sample provided)
• additional materials, depending on extension activities you choose (see More Estimation Practice section of the Lesson Plan)

Lesson Plan

Write the word estimate on a board or chart. Ask students what the word means to them. Write students responses for all to see. Ask a few students to use the word estimate in a sentence. Write those sentences on the board or chart, too. At the end of this introductory activity, students should have a sense that sometimes, especially when dealing with large numbers, it is appropriate to estimate a number. Estimating does not mean counting precisely; instead, it means using some information you know to make a best guess" or an informed guess" -- or to come up with a ballpark figure" -- as to what the large number might be.

Create a chart like the one below. You might provide copies of the chart for students (by drawing it out and photocopying it or by copying/pasting the chart below into a Word document and printing it out). Alternatively, you might draw the chart on a board or chart or project the chart on a screen for students to copy.

 ESTIMATE THE MY BEST ESTIMATE Best guess: Number of kernels on teachers ear of corn (unhusked) Best estimate: Number of kernels on teachers ear of corn (husked, from a distance) Best estimate: Number of kernels on my groups ear of corn (husked) Actual number of kernels on my groups ear of corn

Arrange students into small groups. Provide an ear of corn for each group. (As best you can, try to purchase ears of corn that are similar in size.) Instruct students not to do anything with their ears of corn yet. You should have an ear of corn for yourself, too.

Hold up your ear of corn -- with its husk still on -- for students to see. Have students guess how many kernels will be on the ear of corn and write that number in the first space on the chart. You might let student groups discuss how many kernels might be on the ear but, in the end, each student should write his or her own best guess.

Talk about what a guess" is. Accept students definitions. Students definitions might include phrases such as a best idea of something, without a lot of information."
Next, husk your ear of corn and hold up the husked ear. Give students an opportunity to fill in the second space on the chart after seeing the ear of corn from a distance, without handling it or seeing it up close.
Seeing from a distance might give students a slightly better chance of making a better guess" or of making a fairly good estimate of the number of kernels.
Next, instruct each group of students to husk their ear of corn. Once husked, instruct them to estimate how many kernels of corn are on the ear. Emphasize that estimating does not mean counting precisely. It means making a best guess" or an informed guess" based on some known information. If you see students in any group counting the actual number of kernels, reinforce the meaning of making an estimate.

After the students/student groups have recorded their estimates on the chart, discuss how they came up with those estimates. Ask: What kind of information did you use to make your estimate without actually counting the kernels? Give students an opportunity to share their thought processes. For example, some students might share that they counted the number of kernels in one row on the ear of corn and then counted to number of rows -- and then added or multiplied to come up with their estimate. Others will have arrived at their estimates in different ways.

Finally, give students the opportunity to actually count the number of kernels on their ear of corn. How does that number compare to their estimate? Talk about how making an estimate was a quick and easy way to make a best guess" as to the number of kernels -- and while not a precise number, an estimate is usually much closer to the actual number of kernels than an outright guess" would be.

You might close out this part of the lesson by asking: Which is better, a guess or an estimate? Usually, an estimate is more accurate than a guess.

More Estimation Practice
Set up a series of estimating practice" scenarios. The chart below presents a number of possibilities. Create some of your own based on your classroom/school and students experiences. Students might work on their own or in small groups to come up with their best estimates. After students have made their estimates, discuss the different ways in which they came up with those estimates. Then compare those estimates to the actual numbers.

Note: Depending on the estimation scenarios you set up, you may require some additional materials not listed above in the Materials Needed section. Some scenarios may involve taking students outdoors (e.g., throwing a ball must be done outdoors), to the school library (to estimate the number of books), or other places in close proximity to your classroom.

 ESTIMATE THE MY BEST ESTIMATE Number of students in our school Number of books on our classrooms bookshelves Length of a school bus Distance a ball is thrown Number of gumballs in this jar Number of goldfish crackers in a jar Length of the classroom Number of windows in our school Number of people in this crowd picture Number of oranges in this picture

Online Games: Estimation
You will find some fun online games that will help you teach/reinforce estimation skills. Most of these games can be used in a variety of ways: as whole class activities projected on a screen, in learning centers, as computer lab practice, or on your approved list of Favorite Games for students to play in their spare time.

• Comparison Estimator
• Estimate It
• Estimation Valley Golf (estimating answers to math problems)
• Estimate

Assessment

Assess students based on their understanding of the difference between a guess and an estimate. You might have them write their own explanation of the difference. In addition, you might assess students understanding by checking the estimates they made on their chart vs. the actual numbers.

Lesson Plan Source

EducationWorld.com

Submitted By

Gary Hopkins

National Standards

LANGUAGE ARTS: English
NL-ENG.K-12.3 Evaluation Strategies
NL-ENG.K-12.6 Applying Knowledge
NL-ENG.K-12.7 Evaluating Data
NL-ENG.K-12.12 Applying Language Skills

MATHEMATICS: Number and Operations
NM-NUM.PK-2.3 Compute Fluently and Make Reasonable Estimates
NM-NUM.3-5.3 Compute Fluently and Make Reasonable Estimates
NM-NUM.6-8.3 Compute Fluently and Make Reasonable Estimates
NM-NUM.9-12.3 Compute Fluently and Make Reasonable Estimates

MATHEMATICS: Measurement
NM-MEA.PK-2.2 Apply Appropriate Techniques, Tools, and Formulas to Determine Measurements
NM-MEA.3-5.2 Apply Appropriate Techniques, Tools, and Formulas to Determine Measurements
NM-MEA.6-8.2 Apply Appropriate Techniques, Tools, and Formulas to Determine Measurements
NM-MEA.9-12.2 Apply Appropriate Techniques, Tools, and Formulas to Determine Measurements

MATHEMATICS: Data Analysis and Probability
NM-DATA.PK-2.3 Develop and Evaluate Inferences and Predictions That Are Based on Data
NM-DATA.3-5.3 Develop and Evaluate Inferences and Predictions That Are Based on Data
NM-DATA.6-8.2 Select and Use Appropriate Statistical Methods to Analyze Data
NM-DATA.9-12.2 Select and Use Appropriate Statistical Methods to Analyze Data

MATHEMATICS: Communications
NM-COMM.PK-12.2 Communicate Their Mathematical Thinking Coherently and Clearly to Peers, Teachers, and Others
NM-COMM.PK-12.4 Use the Language of Mathematics to Express Mathematical Ideas Precisely

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