Question:
The sum of three consecutive odd natural numbers is 69. Find the prime number out of these numbers.
Solution:
Let the three consecutive odd natural numbers be $x,(x+2)$ and $(x+4)$. According to the question,
$x+(x+2)+(x+4)=69$ [given]
$\Rightarrow$ $3 x+6=69$
$\Rightarrow$ $3 x=69-6 \Rightarrow 3 x=63$
$\therefore$ $x=63 \times \frac{1}{3}=21$
Thus, the three consecutive odd natural numbers are $21,(21+2)$ and $(21+4), i, e .21,23$ and $25 .$ Out of these, only 23 is the prime number.