Find the $\mathrm{HCF}$ of the following numbers by prime factorisation method:

$84, 120, 138$

Find the $\mathrm{HCF}$ of the following numbers by prime factorisation method:

$81, 117$

Find the $\mathrm{HCF}$ of the following numbers by prime factorisation method:

$630, 1188$

Find the $\mathrm{HCF}$ of the following numbers by division method:

$216, 1176$

Find the $\mathrm{HCF}$ of the following numbers by division method:

$2700, 1728$

Find the $\mathrm{HCF}$ of the following numbers by division method:

$768, 324$

Find the L.C.M. of the following numbers by prime factorisation method:

 $34, 40, 126$

Find the L.C.M. of the following numbers by prime factorisation method:

 $20, 24, 36$

Find the L.C.M. of the following numbers by prime factorisation method:

 $36, 54, 72$