Display the two estimation jars (Jar A and Jar B) that
you prepared prior to the lesson. Show students the
bag of 10 items. See Materials Preparation.
- What is a “crazy” estimate for the number of items
in this jar? Why?
- What is a “could be” estimate?
Introduce Questions 4–7 on the Estimation
Strategies page. Students will estimate the quantities
in the jars and then estimate the sum when the items
in the jars are combined. Before they begin working,
display and direct students’ attention to the Math
Practices page in the Student Activity Book. Tell students
to focus on MPE2, find a strategy.
What are some of the tools and strategies you
could use to estimate the quantity of items in the
jars for Questions 4 and 5? (Possible responses:
use the benchmark bag; think of reasonable could
be numbers and unreasonable crazy numbers)
What are some of the tools and strategies you
could use to find the sum of the items in Jar A and
Jar B for Question 6? (Possible response: We
could use some of the strategies on the class list
like using friendly numbers or counting on by
tens. We could use number lines, calculators, or
the 200 Chart.)
How can you show your work [MPE5]? (We can
use words to tell or drawings to show how we
estimated, explaining the strategies and the numbers
we used.)
Assign Questions 4–6 for students to complete individually.
When all students have finished, tell them
the number of items in Jar A and the number in Jar
B. Combine the quantities in the two jars. Solve the
addition problem together as a class. Write a number
sentence to match the addition situation.
Does that sum sound reasonable? Why do you
think so? (Possible response: The sum is close to
what I estimated it would be in Question 6 so I
think it is reasonable.)
Assign Question 7. Students will record the actual
number of items in the jars when combined and
compare this sum to the estimate they made in
Question 6, checking the reasonableness of their
estimate [MPE3].
Finally, ask students to think about the strategies
they used to estimate the sums and the quantities on
the Estimation Strategies page.
Should we add any new estimation strategies to our list?
Which strategy did you like the best and why?
What made that strategy easy to use?
Which one was the hardest to use and why?
Which strategy was fun to use and why?
Discussing the various characteristics of the strategies
helps students review them. These strategies lay
the foundation for the addition algorithm, and using
them gives students confidence in their answers.
Use Check–In: Questions 4–7 on the Estimation Strategies
pages in the Student Activity Book to assess students’
abilities to estimate the number of objects in a group using
benchmarks [E5]; estimate sums using mental math
strategies [E6]; find a strategy [MPE2]; check for
reasonableness [MPE3]; and show work [MPE5].
Estimate other quantities to provide targeted practice. See
the Meeting Individual Needs Box and Materials Preparation.
