If a:b be the ratio of two whole numbers and c be their HCF then the LCM of these two numbers is:

abc

Ratio of the numbers = a : b

HCF of the numbers  =  c

So, z is the common factor of the numbers

Then, First number  =  ac

Second Number  =  bc

Now,

First Number  ×  Second Number  = HCF × LCM of the numbers

ac × bc = c × LCM

LCM = abc