1. Concrete → Pictorial → Abstract (CPA)
Concrete
Represent quantities physically: counters, linking cubes, base-ten blocks, fraction strips, or actual measurements.
3 × 4: assemble three groups of four cubes.
Pictorial
Translate the situation into a meaningful drawing: arrays, number bonds, bar models, area diagrams or number lines.
3 × 4: draw three groups of four dots.
Abstract
Use symbols and procedures while maintaining the connection to the quantities represented.
For a strong learner: You can start with the abstract problem, then ask the student to reconstruct or interpret the model. Do not insist on manipulatives when understanding is already demonstrated.
2. Number bonds: the whole is the sum of its parts
12 = 7 + 5; 12 − 7 = 5
Why number bonds matter
The same part–whole relationship underlies making ten, regrouping, distributive multiplication, and fractional quantities. Students use quantities flexibly instead of memorizing unrelated tricks.
| Strategy | Example | Underlying property |
|---|---|---|
| Make ten | 8 + 7 = 8 + 2 + 5 = 15 | Part–whole decomposition |
| Compensation | 398 + 257 = 400 + 257 − 2 = 655 | Preserve the sum |
| Equal adjustment | 503 − 198 = 505 − 200 = 305 | Preserve the difference |
| Distribute | 23 × 4 = 20 × 4 + 3 × 4 = 92 | Distributive law |
| Divide in parts | 156 ÷ 6 = 120 ÷ 6 + 36 ÷ 6 = 26 | Decomposition |
3. What to ask before drawing a model
- What is the unknown? Name it in words.
- What is the whole or reference amount? Explicitly identify it.
- How are the known quantities related? Part/whole, difference, multiple, fraction, ratio or change?
- Would a picture make the relationship clearer? Choose a number line, array, bar, or area diagram.
- Which mathematical statement describes the model? Write the operation or equation.
- Does the result satisfy the original problem? Check units and meaning.
4. The five-part tutoring sequence
Diagnose → Connect
Let the student solve an unfamiliar problem in a method of their choice. Ask them to explain why it works. Then connect the reasoning to a pictorial representation.
Extend → Vary → Verify
Present a related but different problem, vary a quantity, and ask for another method. Check independent mastery now and after a delay.
5. Bar models and algebra are complementary
A Grade 5 learner might solve “Sarah has three times as many as John; together they have 72” by writing x + 3x = 72. A bar model gives the same result using four equal units, each worth 18.
The purpose of bar modeling isn't to prohibit algebra. It makes multiplicative structure visible and gives younger students a foundation for algebraic thinking.
6. Diagnose the kind of mistake
| Observation | Possible interpretation | Immediate response |
|---|---|---|
| Computes correctly but draws the wrong model | Representation gap | Match the diagram to the solved equation |
| Adds denominators when adding fractions | Conceptual gap | Use equal-sized fraction strips |
| Uses 240 as the whole in a “fraction of what remains” question | Reference-whole confusion | Draw before and after states |
| Accurate but unusually slow on routine facts | Fluency gap | Practice efficient strategies after understanding |
| Correct answer, weak explanation | Possibly procedural knowledge only | Ask for a second representation and why it works |
| One isolated arithmetic slip | Possible execution issue | Check the pattern before reteaching |
Next: See these ideas in the original visual diagrams.
Bar-model atlas →