Lesson 1

Estimation Strategies

Est. Class Sessions: 2
X

Mathematical Standards

2.NBT.A
Understand place value. (2.NBT.A.1, 2.NBT.A.4)
2.NBT.B
Use place value understanding and properties of operations to add and subtract. (2.NBT.B.8, 2.NBT.B.9)

Standards for Mathematical Practice

MP2.
Reason quantitatively.
MP4.
Model with mathematics.
MP5.
Use appropriate tools strategically.
MP6.
Attend to precision.

In Part 1, students practice estimating the number of objects in a group using a sample or benchmark collection, and by identifying “could be” and “crazy” estimates. In Part 2, students estimate the total cost of two items using computational estimation. Students assess both the reasonableness of their estimates and of their answers by comparing the two.

Content in this Lesson

  • Estimating the number of objects in a group [E5].
  • Estimating sums using mental math strategies [E6].
  • Using estimation to determine the reasonableness of a solution to an addition problem [MPE3].
  • Choosing good tools and efficient strategies to estimate quantities and
    sums [MPE2].
  • Showing work [MPE5].
X

Materials for Students

Daily Practice and Problems Lesson Homework Assessment

Student Books

 Student Activity Book

Teacher Resources

 Teacher Guide - digital

Supplies for Students

desk number line (0–100)

Supplies for Student Pairs

calculator

Materials for the Teacher

Display of Price Cards page (Student Activity Book) Page 319
Display of Math Practices (Student Activity Book) Reference
Unit 7 Assessment Record
Math Facts Class Record

“Keepin’ Count” poem from Falling Up by Shel Silverstein
2 identical jars of 50–100 items. See Materials Preparation.
referent bag of 10 items. See Materials Preparation.
2 chains of 50–100 connecting links each. See Materials Preparation.
chain of 10 connecting links. See Materials Preparation.
resealable plastic bags
chart paper
calculator
other small items, optional

Materials Preparation

Prepare Estimation Jars and Referent Bag. Find two identical jars. Fill one jar with 50–100 small, identical items (e.g., cubes, links, paper clips). Label this Jar A. Fill a second jar with a different amount of 50–100 of the same item. Label this Jar B. Keep track of the number of items in each jar. Make a sample or referent bag using 10 of those items in a resealable plastic bag.

Make Connecting Link Chains. Make two long chains of 50–100 connecting links each. The chains should be different lengths and different colors, for example, a chain of 72 red links and another of 55 blue links. Keep track of the number of links in each chain. If you do not have links, large paper clips can be used. However, because the paper clips are of the same color, you must mark where one chain ends and the other begins with tape when the chains are combined. Make a short chain of 10 connecting links or large paper clips for students to use as a benchmark.

Determine the Number of 2nd-Graders in School. Students will need to know the number of second-graders in the school so that they can compare their estimates to the actual number. If there is only one second-grade class, you may choose to alter the task to estimating the number of students in the whole school.

Prepare Guessing Jars for Optional Targeted Practice. Create a learning center by placing 50–100 small items in a jar and a referent bag of 10 items in a learning center. Allocate a display space for students to write and organize their estimates.

Triangle Flash Cards. Prepare copies of the Triangle Flash Cards on heavier paper or card stock. Have students cut apart each set and store them in an envelope. Provide each student with two sets, one to use at school and one to take home. Students will need these cards on an ongoing basis.

Assessment in this Lesson

ASSESSMENT EXPECTATION ASSESSED MATH PRACTICES EXPECTATION ASSESSED
Estimation Strategies
Check-In: Questions 4–7 with Feedback Box
Student Activity Book
Pages 322–324
E5.
Estimating the number of objects in a group using benchmarks.
E6.
Estimate sums using mental math strategies (e.g., rounding using benchmarks, using friendly numbers, composing and decomposing numbers, counting on).
MPE2.
Find a strategy. I choose good tools and an efficient strategy for solving the problem.
MPE3.
Check for reasonableness. I look back at my solution to see if my answer makes sense. If it does not, I try again.
MPE5.
Show my work. I show or tell how I arrived at my answer so someone else can understand my thinking.
DPP Item A
Triangle Flash Cards:
Group E
Teacher Guide - digital
E7.
Demonstrate fluency with the addition facts in Group E (5 + 7, 8 + 4, 8 + 5, 9 + 3, 9 + 4, 9 + 5, 10 + 1, 10 + 2,
10 + 3).
DPP Item C
Adding Nine
Teacher Guide - digital
E7.
Demonstrate fluency with the addition facts in Group E (5 + 7, 8 + 4, 8 + 5, 9 + 3, 9 + 4, 9 + 5, 10 + 1, 10 + 2,
10 + 3).
E8.
Determine the unknown number in an addition or subtraction sentence relating three whole numbers for the facts in Group E.