Prime Time
NCERT Ganita Prakash for Class 6, Chapter 5, Prime Time, starts with the idli vada game of calling common multiples of two numbers. It defines factors and multiples, separates prime numbers with exactly two factors from composite numbers, and hunts primes to one hundred with the Sieve of Eratosthenes. Divisibility tests for two, three, four, five, six, eight, nine, ten, and eleven speed up checking. Prime factorisation then finds highest common factors, lowest common multiples, and co prime pairs.
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