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Teaching video
A teaching recording for this chapter has not been published yet. Start with the worked example below and explore the related animations where available.
Grade 4 chapters and video availability01 · Read and understand
What you will learn
- Distinguish prime, composite, and the number one.
- Explain your method and check what the result means in the stated situation.
Before you start
Multiplication and division facts, simple fractions, place value, and basic length and area measurement.
Keep paper nearby. Read the question once for the context, then again to identify what is known and what you need to find.
Start with a question
Classify 13, 15, and 1 by their positive factors.
Why this math matters
Use factor structure to sort whole numbers and prepare for fraction simplification. The worked example shows how to connect the situation, its mathematical representation, and a check on the result.
Set up the model
A useful answer starts with clear assumptions:
- Use the units, grouping rules, and reference whole stated in the question.
- Treat the supplied counts and measurements as exact within the classroom model, unless an estimate or a random outcome is requested.
02 · Work through the example
Follow the reasoning, one step at a time.
Try to predict the next step before reading it. After each calculation, explain why the operation makes sense and how it helps answer the original question.
Work through it with Amar
See this example unfold.
The complete worked example, one idea at a time.
Classify numbers by their factors
PausedQuestion: Start with the question. Paused.
Question
Start with the question
Classify 13, 15, and 1 by their positive factors.
Before you calculate
Read what is known and what you need to find. Make a prediction before moving to the first calculation.
Starts paused. Play advances through the full text at a reading pace; pause whenever you need more time. Previous, Next, and the phase buttons let you set your own pace. Playback pauses when this walkthrough leaves the screen or you switch tabs.
Your device’s reduced-motion setting keeps each phase still. Manual controls remain available. The full written solution stays below.
Represent the situation
13: factors 1 and 13
Exactly two positive factors makes thirteen prime.
Connect the parts
15: factors 1, 3, 5, 15
More than two positive factors makes fifteen composite.
State and check the result
1 is neither prime nor composite
One has only one positive factor, so it meets neither definition.
The result
1 is neither prime nor composite
One has only one positive factor, so it meets neither definition.
Common mistakes to catch
- One is not prime.
- Oddness alone does not establish primality.
03 · Practice independently
Try it before revealing the answer.
Use paper or a calculator as needed. Write your units and reasoning, then open the hint or explanation to check your approach.
Practice 1
Is 2 prime?
Show a hint
List its positive factors.
Reveal answer and explanation
Yes
Its only factors are one and two; it is the only even prime.
Practice 2
Is every odd number greater than one prime?
Show a hint
Test nine.
Reveal answer and explanation
No
Nine is odd but equals three times three.
Take the idea with you
Use factor structure to sort whole numbers and prepare for fraction simplification.
04 · Reflect and continue
Can you explain it in your own words?
Before moving on, explain the main idea without looking at the worked example. Try both practice questions, check your reasoning, and name one mistake you now know how to avoid. Return to a step if you still need support.
Up next: A pattern can multiply each step
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