Prime Time: Seeing How Numbers Are Built
Distinguish factors, multiples and primes by examining the structure of whole numbers.
A number can be viewed as a quantity and also as something that can be arranged into equal groups. Twelve counters can form a 1 by 12 rectangle, a 2 by 6 rectangle or a 3 by 4 rectangle. These arrangements reveal factor pairs. They offer a way to discuss divisibility through structure, alongside learning multiplication facts.
A prime number is a positive integer greater than 1 with exactly two positive factors: 1 and itself. A composite number has more than two positive factors. The number 1 is neither prime nor composite because it has only one positive factor. Two is prime and is the only even prime: every larger even number also has 2 as a factor.
Take 12 apart into prime factors. One route is 12 = 3 × 4 = 3 × 2 × 2. Another is 12 = 2 × 6 = 2 × 2 × 3. The order differs, but the prime factors are the same. Every integer greater than 1 has a unique prime factorisation apart from the order of its factors. A factor tree is useful when the student understands why the branches must multiply back to the starting number.
Factors and multiples answer different questions. Three is a factor of 12 because 3 × 4 = 12. Twenty-four is a multiple of 12 because 12 × 2 = 24. Ask the student to show the multiplication relationship when the words become confusing. This meaning can later support work with common factors and common multiples; it does not remove the need for practice.
Source & further reading
The number examples are self-contained mathematical explanations. Further reading on helping students connect representations, concepts and notation: IES problem-solving guide.
IES: Improving Mathematical Problem Solving in Grades 4 Through 8Prepared with AI-assisted research and writing. Sources support the attributed factual statements; explanatory framing and practical suggestions are Dishantra’s interpretation. No independent expert review is claimed. Editorial standards · Corrections & support
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