To conclude the lesson, ask students to consider the strategies they used to solve the decimal addition and subtraction problems in the lesson.
Ask questions such as the following:
- Which is your favorite decimal addition strategy to use? Why?
- Is your favorite subtraction strategy different from your favorite addition strategy?
- Does one way help you solve the problem more quickly? (Possible response: Because I understand how to use the paper-and-pencil methods, they are generally more efficient than using base-ten pieces or fraction circle pieces. It is convenient because I don't need any tools like hundredths grids or hundredths circles.)
- Do you have questions about a certain strategy on the menu you created?
- Talk with a partner. Explain a method for adding and subtracting decimal numbers that you can use with any two numbers. (Possible response: Line up the numbers so that the decimal points are underneath each other. Then like place values will be aligned. You add or subtract all the digits in like places. For example, you add tenths to tenths, or subtract hundredths from hundredths. You place the decimal point underneath the numbers you added or subtracted, keeping it aligned with the decimal points in the problem.)
Assign the Add and Subtract Decimals Quiz Assessment Masters for students to complete individually. Students may use any tools used in the lesson as they complete the assessment. Have copies of the Decimal Number Lines, Decimal Grids, and Hundredths Circles Masters available. Students can attach the copies that they use to their quizzes to show their work.
Use the Add and Subtract Decimals Quiz Assessment Masters with the Feedback Box to assess students' abilities to represent numbers to the thousandths using symbols, area models, base-ten pieces, and number lines [E1]; compare decimals to the thousandths using place value understanding [E3]; add and subtract decimals to the hundredths using models and strategies [E7]; estimate decimal differences [E9]; and find a strategy [MPE2].
Students can play the Add or Subtract to 1 Game for targeted practice. Students can use their own deck of Digit Cards 0–9 or the display deck you prepared prior to the lesson. They can reuse the Add or Subtract to 1 Game Board from the Add or Subtract to 1 Game pages from the Student Activity Book.
