Near 100 Strategies (99, 101, 25×4) (828)

Teaching Notes

These strategies build number sense and mental math fluency. Emphasize the why behind each trick.

Vocabulary

Strategy: A plan to solve a problem.

Compensate: Make up for a difference.

Common Mistakes

• Subtracting wrong amount for 99×n
• Forgetting to adjust for 99/101
• Miscalculating 25x multiples
• Basic arithmetic errors
• Not seeing the pattern

Differentiation

Discussion Questions

• Why does 101 × n = 100 × n + n work?
• When is the 25 × 4 trick most useful?
• How do these strategies save time?
• Can you invent another similar strategy?

Extension Activities

• Multiply by 101.
• Use 25 x 4 strategy.
• Estimate products near 100.

Parent Tip

Ask your child to estimate prices near $100, like $99.

Skill Cluster

Number Sense & Mental Math

Estimated Time

12 minutes

Skills Practiced

Prerequisites

• 821
• 827
• Basic multiplication facts
• Understanding place value
• Distributive property concept

Next Steps

• Multi-digit multiplication
• Estimation strategies
• Algebraic thinking for properties
• Distributive Property Multiplication
• Mental Math with Multiples of 10
• Estimation Strategies for Products