Question

Find the odd one out in the given options:

• A. $145$
• B. $197$
• C. $325$
• D. $399$

Answer 1

The correct option is D

$399$

Evaluate the odd one out:

The given numbers are,

$145,197,325,399$

Here, we can observe that three of these four numbers are equal to a perfect square plus one but one of them is equal to a perfect square minus one.

$\therefore$For $145$ we get, $145=144+1={\left(12\right)}^2+1$

For $197$ we get, $197=196+1={\left(14\right)}^2+1$

For $325$ we get, $325=324+1={\left(18\right)}^2+1$

But, for $399$ we can see that $399=400-1={\left(20\right)}^2-1$.

Therefore $399$ is the odd one in this series.

Hence option $\left(\mathrm{D}\right)$ is the correct answer.