3-Digit Addition · Regroup in Consecutive Places · Horizontal

Teaching Notes

Focus: Three-Digit Addition: Regroup in Consecutive Places. 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

1. Read each number by place value.
2. Add the ones, then the tens and any remaining places.
3. When a column totals ten or more, exchange ten units for one unit in the next place.
4. Record the carried amount before continuing.
5. In a horizontal problem, you may rewrite the numbers vertically; the ones must still line up.

Worked Examples

Evaluate 278+356.

1. Place value 1: 8 + 6 = 14. Write 4 and carry 1 to the next place.
2. Place value 10: 7 + 5 + 1 carried = 13. Write 3 and carry 1 to the next place.
3. Place value 100: 2 + 3 + 1 carried = 6. Write 6.

Answer: 634

Common Mistakes and How to Help

A carried ten belongs in the next column. Do not write a two-digit total into a single place or forget to include a carry in the next sum.

Subtract one addend from the sum. The result should equal the other addend.

Questions to Check Understanding

• Subtract one addend from the sum. The result should equal the other addend.
• 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.