Grade 3/Measurement
Convert Centimeters and Millimeters (668)
Convert between centimeters and millimeters using whole numbers. Students learn that 10 millimeters equals 1 centimeter, practicing metric system conversions with simple divisible numbers that result in whole number answers.
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Quick Tip
10 mm = 1 cm
Teacher Resources
Teaching Notes
10 millimeters = 1 centimeter. Metric conversions use powers of 10, making them easier than customary. Use metric rulers showing both units.
Vocabulary
Centimeter: A metric unit of length.
Millimeter: A smaller metric unit of length.
Common Mistakes
- Confusing with other metric conversions
- Place value errors with 10
- Mixing up multiplication/division
- Incorrectly applying the 10:1 ratio
- Forgetting units in answers
Differentiation
SupportUse metric ruler. Show that moving decimal point works for 10s.
ChallengeMix with other metric units. Compare ease of metric vs customary conversions.
Discussion Questions
- Why is metric easier?
- What countries use metric exclusively?
- When is it better to use centimeters?
- When is it better to use millimeters?
- How is this conversion like multiplying by 10?
- Can you name other metric units of length?
Extension Activities
- Compare metric and customary rulers
- Research metric system history
Parent Tip
Use a ruler to show centimeters and millimeters on everyday objects.
Learning Path
Skill Cluster
Measurement & Data
Estimated Time
12 minutes
Skills Practiced
metric conversioncentimeters millimetersplace value
Prerequisites
- 666
- Measuring Length in Centimeters
- Multiplying by 10
- Dividing by 10
Next Steps
- Convert Meters and Centimeters
- Compare Metric Lengths
- Measuring with Centimeters
- Measuring with Millimeters
- Metric Conversions: Meters and Centimeters