Question:
Which of the following is a rational number?
(a) $\sqrt{2}$
(b) $\sqrt{23}$
(c) $\sqrt{225}$
(d) $0.1010010001$
Solution:
(c) $\sqrt{225}$
Because 225 is a square of 15 , i.e., $\sqrt{225}=15$, and it can be expressed in the $\frac{p}{q}$ form, it is a rational number.