Find which of the variables $x, y, z$ and $u$ represent rational numbers and which irrational numbers.
(i) $x^{2}=5$
(ii) $y^{2}=9$
(iii) $z^{2}=0.04$
(iv) $u^{2}=17 / 4$
(i) Given, $x^{2}=5$
On taking square root both sides we get
$x=\pm \sqrt{5}$ [irrational number]
(ii) Given, $y^{2}=9$
On taking square root both sides, we get
$y=\pm \sqrt{9}=\pm 3$ [rational number]
(iii) Given, $z^{2}=0.04$
On taking square root both sides, we get
$z=\sqrt{0.04}=\sqrt{\frac{4}{100}}=\frac{2}{10}$ [rational number] $\left[\because \frac{p}{q}\right.$ form, $q \neq 0, p$ and $q$ are integers $]$
(iv) Given, $u^{2}=\frac{17}{4}$
On taking square root both sides, we get
$u=\pm \sqrt{\frac{17}{4}}=\pm \frac{\sqrt{17}}{2}$ [irrational number because numerator is irrational]