Question

how to find lcm and hcf of fractions

Answer 1

Although Least Common Multiple and Greatest Common Divisor(also known as Highest Common Factor) are defined for integers, the same logic can be applied to rational numbers as well. 
            The LCM of 2 fractions is the LCM of the numerators upon GCD of the 2 denominators. Suppose a/b and p/q are 2 fractions, where a,b,p,q are integers. Then the LCM of the fractions is lcm(a,p)/gcd(b,q). 
            Similarly GCD of 2 fractions is the GCD of the numerators upon the LCM of denominators. The GCD of the same a/b and p/q is gcd(a,p)/lcm(b,q).
            For example, let us take the fractions 66/5, 44/25.
lcm(6/5,4/25)= lcm(6,4)/gcd(5,25)=1212/5
gcd(6/5,4/25)=gcd(6,4)/lcm(5,25)=22/25
            Note that the fractions have to be in their simplest form.