Question

find the HCF and LCM of 420 and 18

Answer 1

you already have
\[420=2^2\times 3\times 5\times 7\]
\[18=2\times 3^2\] so greatest common factor is
\[2\times 3=6\] and least common multiple is
\[2^2\times 3^2\times 5\times 7\] whatever that is