PS 42X Grade 5 Unpacking Chapter 3

Chapter 3 Adding and Subtracting Decimals

Pre-assessment: Find out which of your students can regroup when adding and subtracting fluently with whole numbers. Find out who can tell how many tens are in the number 1,456 and explain why.

Do not write the numbers on the place value chart on a diagonal.

Use measurement to help students see thousandths. For example, a millimeter is 1/1000 of a meter. It takes 1000 millimeters to make a 1 meter. Say: “If our meter is a whole, kind of like 1 whole dollar bill, how would we represent that on the place value chart?” Have students make using register tape. This is a linear model. 

Materials: Money, base-ten blocks (area model) or decimal squares

  • Lesson 3.1: Use Kagan strategy of Quiz, Quiz, Trade or Find Someone Who.
  • Lesson 3.2: Make an anchor chart and game with the students that show different representations of numbers by place. Ensure that you name the different ways to show numbers, e.g. standard form, expanded form by place value, expanded form using decimal fractions, expanded form using exponents, using multiplication by place value, word form, unit form, etc. Make this into a center.
  • Lesson 3.3: Ways to compare decimals: By position in a place value chart, by expanded form, placement on a number line, multiply by 10, 100 or 1000 to make into whole numbers, using pictures or concrete objects, etc.
  • Lesson 3.4: Use a number line! See link for ITPs Decimals. Do not teach the traditional procedure. Make students reason out what is happening. Make compare decimals into a center and do a Quiz, Quiz, Trade.
  • Have a day of centers to revisit concepts 3.1 – 3.4. Do a guided group with Tier 2 or 3 students on addition of decimals using concrete materials. You are getting ready for Lesson 3.5. Have a center where you shift the whole and reposition the base-ten blocks redefine the whole.
  • Lesson 3.5 & 3.6, 3.8 & 3.9: Spend 2 days on each of these topics and explicitly included examples, when regrouping is going to be involved. Student must act out all the problem, sketch and place in a context. Turn the “Advanced Learners” on pg. 182 into a center activity to revisit all year long.

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