While adding or subtracting two rational numbers having different denominators, how will you make the denominators equal?

To add or subtract two rational numbers with different denominators, we make the denominators equal by finding the L.C.M. (Least Common Multiple) of the two denominators.

Steps to follow :

1. Find the L.C.M. of the two denominators.

2. Convert each rational number into an equivalent rational number whose denominator is the L.C.M.

3. Add or subtract the numerators while keeping the common denominator.

Example : Add $\dfrac{2}{3}$ and $\dfrac{1}{4}$.

L.C.M. of 3 and 4 = 12.

$\Rightarrow \dfrac{2}{3} = \dfrac{2 \times 4}{3 \times 4} = \dfrac{8}{12} \\[1em] \Rightarrow \dfrac{1}{4} = \dfrac{1 \times 3}{4 \times 3} = \dfrac{3}{12} \\[1em] \Rightarrow \dfrac{8}{12} + \dfrac{3}{12} = \dfrac{11}{12}.$

Hence, we make the denominators equal by taking the L.C.M. of the denominators.