Primary Standards:

MAFS.5.NBT.2.7: Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

Connecting Standards:

MAFS.5.NBT.1.3: Read, write, and compare decimals to thousandths.

  1. Read and write decimals to thousandths using base-ten numerals, number names, and expanded form, e.g., 347.392 = 3 × 100 + 4 × 10 + 7 × 1 + 3 × (1/10) + 9 × (1/100) + 2 × (1/1000).

Content Knowledge:

In 4th grade, students extended their place value understanding to include decimals.  In this Unit, students apply their decimal understanding, and extend understanding of addition and subtraction of whole numbers, to add and subtract decimals to the hundredths.  Rather than being introduced to these processes with a standard algorithm, students begin this exploration by using what they know about place value to add tenths to tenths and hundredths to hundredths.  These experiences increase students’ number sense related to decimals.

The use of concrete models and drawings allows students to visualize the addition and subtraction process based on place value understandings.  Models may include base-ten block, 10-by-10 grids, drawings, and place value charts.  As with any computation, students should be able to justify whether their answers are reasonable.  It is essential to ask students to use their understanding of decimals to estimate sums or differences prior to computation.  Estimation and reasonableness should be embedded in all tasks.


GCG 1 – Learning Goal:  As a mathematician, I will be able to model addition of decimals

  • Step 1: Use rounding to estimate sums of decimals (make connections to whole number rounding strategies)
  • Step 2: Use base ten models and place value understanding to add decimals (to the hundredths) with and without regrouping
  • Step 3: Relate addition models to a written method and explain sums using place value vocabulary

GCG 2 – Learning Goal:  As a mathematician, I will be able to model subtraction of decimals

  • Step 1: Use rounding to estimate differences of decimals (make connections to whole number rounding strategies)
  • Step 2: Use base ten models and place value understanding to subtract decimals (to the hundredths) with and without regrouping
  • Step 3: Relate subtraction models to a written method and explain differences using place value vocabulary

GCG 3 – Learning Goal:  As a mathematician, I will be able to solve problems with addition & subtraction of decimals

  • Step 1: Solve one step word problems involving addition and subtraction of decimals
  • Step 2: Solve two step word problems involving addition and subtraction of decimals