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CHAPTER AT A GLANCE
Prime Time
•Unit: Number System
•Board weightage: Multiples and factors, prime and composite numbers, Sieve of Eratosthenes, co-prime numbers, prime factorisation and divisibility tests for 2, 4, 5, 8 and 10 give regular 1-mark, 2-mark, 3-mark and 4-mark questions in school examinations (please check your school's latest sample paper)
•Key ideas from the textbook: common multiples and common factors (idli-vada and treasure games), prime and composite numbers, twin primes, co-prime pairs, prime factorisation and its uniqueness, checking divisibility through prime factorisation, divisibility tests
•Most scoring part: writing the complete prime factorisation, listing all factors without missing any, and applying the divisibility rule with the correct digits
•Time to revise: about 60 minutes
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