Decimal Addition · Hundredths, Regrouping · Horizontal
Focus: Adding Hundredths: Regrouping. Use the worked example and teaching sequence below to explain the reasoning before independent practice.
Use New Numbers to make another set. Choose Worksheet or Answer Key, then use the worksheet’s Print button.
Teaching Notes
Focus: Adding Hundredths: Regrouping. Use the worked example and teaching sequence below to explain the reasoning before independent practice.
Before You Begin
- Read the numbers and identify the operation.
Teaching Steps for Parents and Teachers
- Line up decimal points so that ones, tenths, and hundredths match.
- Add trailing zeros if they help you see the places; this does not change a number.
- Add from the smallest place shown and regroup as needed.
- Put the decimal point in the sum directly below the other decimal points.
Worked Examples
Evaluate 2.78+1.65.
- Align the decimal points so corresponding places line up.
- Use trailing zeros if needed, then calculate one place at a time.
- 2.78 + 1.65 = 4.43
Answer: 4.43
Common Mistakes and How to Help
Align decimal points, not the right-hand ends of the numbers. For example, a tenth must not be added to a hundredth merely because both digits happen to be last.
Subtract either addend from the sum. Estimate with nearby whole numbers to check the size of the answer.
Questions to Check Understanding
- Subtract either addend from the sum. Estimate with nearby whole numbers to check the size of the answer.
- Which step explains your answer?
- Can you apply the same reasoning when the numbers change?
Practice Advice
Work through the example together. Ask the learner to explain the first two problems, then try three independently. Review the first incorrect step before assigning more practice.
Next Practice
- Use New Numbers to practice the same skill with different values.
- If the learner needs help, return to the example and model each step before trying again.