1.Classify the following numbers as rational or irrational :
i)$$2 - \sqrt{5}$$
ii)$$(3 + \sqrt{23}) - \sqrt{23}$$
iii)$$2\sqrt{7} / 7\sqrt{7}$$
iv)$$1 / \sqrt{2}$$
v)$$2\pi$$
Therefore, $$2 - \sqrt{5}$$ is an irrational number.
ii)$$(3 + \sqrt{23}) - \sqrt{23}= 3$$ i.e. rational number .
iii) $$2\sqrt{7} / 7\sqrt{7} = 2/7$$ i.e. rational number
iv) $$1 / \sqrt{2}$$ is an irrational number because, as numerator is a rational number but denominator is an irrational number.
v) $$2\pi$$ is a Irrational number , since 2 is a rational number and $$\pi$$ is an irrational number.