Adding Multidigit Numbers

Est. Class Sessions: 2–3

Developing the Lesson

Part 2: Choose a Strategy

Correct Confused Contessa's Mistakes. Display and direct students to the Help Her Fix It pages in the Student Activity Book. Explain to the students that Confused Contessa needs help correcting mistakes she made while adding larger numbers. For each problem, ask students to estimate the sum and then discuss Contessa's work with a partner to try to identify her mistake.

Then ask:

Can you explain the mistake Contessa made?
Solve the problem correctly using the same method Contessa used.
Show us how to solve the problem correctly.

Discuss the mistakes Contessa made in Questions A–F:

place value mistakes; Contessa did not list the correct value for the numbers.
recording mistakes; The value for the numbers is correct, but Contessa needed to align and add hundreds to hundreds, tens to tens, and ones to ones.
Contessa did not regroup.
Contessa regrouped unnecessarily.
place value mistakes; Contessa added the digits and then recorded them all as hundreds.
regrouping mistake; Contessa forgot to regroup and overlooked adding another ten and another hundred.

Apply Strategies to Solve Word Problems. Display and direct students' attention to the Math Practices page in the Student Activity Book Reference section. As they work on the multidigit addition problems on the Shark Day pages in the Student Activity Book, students will apply the following Math Practice Expectations.

In preparation, ask:

MPE1 is Know the problem. How will you know what is important when solving these word problems? (Read the problem carefully; think about what the question is asking and what I need to find out.)
MPE2 is Find a strategy. Which of the tools and strategies on the Addition Strategies Menu can you use? (any of them except for the 200 Chart if the numbers are very large; Some strategies are better than others depending on the problems.)
MPE3 is Check for reasonableness. How does estimating the sum first help you check for reasonableness? (You can compare your estimate to your answer to see if it makes sense. If it doesn't, you can solve it again.)
MPE5 is Show my work. What is important to remember when you are showing or telling how you arrived at your answer? (It is important to record my steps clearly so that others can understand my thinking.)
MPE6 is Use labels. Why is this important? (It is important so that it is clear what the numbers in your answer mean.)

Tell students to refer to the Addition Strategies Menu in the Student Activity Book Reference section as they complete the word problems on the Shark Day pages. See Figure 4.

Use Check-In: Questions 4–5 with the Feedback Box on the Shark Day pages in the Student Activity Book to assess students' abilities to add multidigit numbers using mental math strategies [E6] and paper-and-pencil methods [E7]; estimate sums [E8]; know the problem [MPE1]; find a strategy [MPE2]; use estimation to check for reasonableness [MPE3]; show work [MPE5]; and use labels [MPE6].