Classify the following numbers as rational or irrational with justification:
$(i)$ $\sqrt{196}$
$(ii)$ $3\sqrt{18}$

(N/A) $(i)$ $\sqrt{196} = 14$. Since $14$ can be expressed in the form $\frac{p}{q}$ where $p, q$ are integers and $q \neq 0$ (i.e.,$\frac{14}{1}$),it is a rational number.
$(ii)$ $3\sqrt{18} = 3\sqrt{9 \times 2} = 3 \times 3\sqrt{2} = 9\sqrt{2}$. Since $\sqrt{2}$ is an irrational number and the product of a non-zero rational number and an irrational number is always irrational,$9\sqrt{2}$ is an irrational number.