Adding whole tens (4 addends) (213)

Teaching Notes

Introduce pairing strategy: add numbers that make friendly sums (like two 50s). Show multiple approaches: left to right, pairing compatible numbers, or making tens. This builds flexibility in mental math strategies.

Vocabulary

Whole tens: Numbers like 10, 20, 30, ending in zero.

Addend: A number added in an addition problem.

Common Mistakes

• Losing track of all four numbers
• Adding only three numbers
• Making calculation errors with larger sums
• Not organizing numbers strategically
• Forgetting to carry over or group tens correctly when adding larger sums.
• Miscounting when skip-counting by tens.
• Treating the '0' in tens as an additional addend instead of recognizing the value of the 'ten' unit.

Differentiation

Discussion Questions

• How is adding multiples of ten similar to adding single-digit numbers?
• What strategy did you use to add the tens quickly?
• If you had 10 tens, how much would that be? How does this relate to place value?

Extension Activities

• Add 5 whole tens.
• Add 3 whole tens.
• Use base-ten blocks.

Parent Tip

Have your child count groups of 10 objects, then combine the groups.

Skill Cluster

Number Sense & Operations

Estimated Time

15 minutes

Skills Practiced

Prerequisites

• Counting by tens
• Adding single-digit numbers
• Understanding place value (tens and ones)

Next Steps

• Adding two-digit numbers (without regrouping)
• Adding two-digit numbers (with regrouping)
• Adding multiple two-digit numbers