Three-Addend Mental Sums (1- & 2-Digit) (753)

Teaching Notes

Have students circle pairs that make ten or hundred.

Common Mistakes

• Forgetting make-ten pairs.
• Miscarrying tens mentally.
• Ignoring mental strategies.
• Adding left-to-right.

Differentiation

Discussion Questions

• How do make-ten pairs help simplify addition?
• What other friendly sums did you find?
• Can you explain your mental strategy?
• When is this strategy most useful?

Skill Cluster

Number Sense & Operations

Estimated Time

12 minutes

Skills Practiced

Prerequisites

• 3
• Adding 1-Digit Numbers
• Making Ten
• Adding Two 2-Digit Numbers

Next Steps

• Adding 3-Digit Numbers (3 Addends)
• Adding Multi-Digit Numbers
• 2-Digit Addition (Regrouping)
• 3-Digit Addition (No Regrouping)
• Mental Math Strategies (Addition)