Mental Math: Adding and Subtracting 10 or 100
Students will mentally add or subtract 10 or 100 to a given number 100-900.
Key Questions
- Explain the pattern that occurs when you add 10 to a number.
- Predict the result of subtracting 100 from a three-digit number.
- Justify how understanding place value helps with mental addition/subtraction of 10 or 100.
Ontario Curriculum Expectations
Suggested Methodologies
Ready to teach this topic?
Generate a complete, classroom-ready active learning mission in seconds.
Planning templates for Mathematics
5E Model
The 5E Model structures lessons through five phases (Engage, Explore, Explain, Elaborate, and Evaluate), guiding students from curiosity to deep understanding through inquiry-based learning.
unit plannerMath Unit
Plan a multi-week math unit with conceptual coherence: from building number sense and procedural fluency to applying skills in context and developing mathematical reasoning across a connected sequence of lessons.
rubricMath Rubric
Build a math rubric that assesses problem-solving, mathematical reasoning, and communication alongside procedural accuracy, giving students feedback on how they think, not just whether they got the right answer.
More in Number Sense and Place Value Patterns
Understanding Place Value to 100
Students will identify the value of digits in two- and three-digit numbers using base ten blocks and place value charts.
3 methodologies
Extending Place Value to 1000
Students will extend their understanding of place value to include hundreds, representing numbers up to 1000.
2 methodologies
Comparing Numbers to 1000
Students will compare two three-digit numbers based on meanings of the hundreds, tens, and ones digits, using >, =, and < symbols.
2 methodologies
Ordering Numbers and Number Sequences
Students will order a set of numbers and identify patterns in number sequences, including skip counting.
2 methodologies
Even and Odd Numbers
Students will identify even and odd numbers up to 20 and explain their properties.
2 methodologies