Question

Which of the following is an irrational number?

Answer 1

0.78 bar = 0.788888...

Note that the decimal expansion of an irrational number is non terminating and non repeating.

But, since the above decimal expansion is non terminating and repeating, this is not an irrational number.

$(\sqrt{12}) ^{2} =12$ which is rational.

$\sqrt{169} =\sqrt{13^{2} } =13$ and hence, a rational number

$\sqrt{18} =\sqrt{9(2)} =3\sqrt{2}$ is an irrational number.