REET Level 1 study notes
Prime and Composite Numbers, LCM and HCF
REET Level 1 candidates should prepare this topic as primary arithmetic, not advanced number theory. The RBSE mathematics syllabus directly names prime and composite numbers, prime factors, Lowest Common Multiple and Heighest Common Factor. The classroom route is factors, multiples, common factors and common multiples through objects, arrays, number lines and small prime factor trees. A prime number has exactly two factors; a composite number has more than two. The HCF is the greatest common factor; the LCM is the least common multiple. Good teaching catches traps such as calling 1 prime, treating every odd number as prime, and reversing HCF with LCM.
Key points
- RBSE directly names prime and composite numbers, prime factors, LCM and HCF in the Level 1 Mathematics syllabus.
- The official RBSE excerpt preserves source spellings such as Heighest in the syllabus anchor.
- A prime number is greater than 1 and has exactly two factors: 1 and itself.
- A composite number is greater than 1 and has more than two factors.
- The number 1 is neither prime nor composite; 2 is the smallest and only even prime.
- HCF is the greatest common factor, so it belongs to factor lists.
- LCM is the least common multiple, so it belongs to multiple lists.
- Prime factorisation helps find HCF by common prime factors and LCM by all required prime factors.
- Classroom teaching should move from objects and arrays to lists and symbols.
- Inclusive examples let every child participate through pointing, speaking, arranging, jumping or writing.
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Study notes
Study focus
REET Level 1 candidates should prepare this topic as primary arithmetic, not advanced number theory. The RBSE mathematics syllabus directly names prime and composite numbers, prime factors, Lowest Common Multiple and Heighest Common Factor. The classroom route is factors, multiples, common factors and common multiples through objects, arrays, number lines and small prime factor trees. A prime number has exactly two factors; a...