Question

Check whether $5\sqrt{2}$ is an irrational numbers are not?

Answer 1

$5\sqrt{2}$

Here 5 is a rational number

But $\sqrt{2}=\mathrm{1.4142....},$ is an irrational number

Then product of an irrational and rational number is also an irrational number

So $5\sqrt{2}=5\times \mathrm{1.4142..}=\mathrm{7.0710...}$ is an irrational number