Question

find the LCM of 21 and 28 by
prime factorisation method.
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Answer 1

$21 = 3 \times 7 \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 28 = 2 \times 2 \times 7 = {2}^{2} \times 7$

LCM(ALL BASE WITH HIGHEST POWER)

=3×7×2^2

=3×7×2×2

=84