Question:
The sum of a natural number and its reciprocal is $\frac{65}{8}$. Find the number.
Solution:
Let the natural number be x.
According to the given condition,
$x+\frac{1}{x}=\frac{65}{8}$
$\Rightarrow \frac{x^{2}+1}{x}=\frac{65}{8}$
$\Rightarrow 8 x^{2}+8=65 x$
$\Rightarrow 8 x^{2}-65 x+8=0$
$\Rightarrow 8 x^{2}-64 x-x+8=0$
$\Rightarrow 8 x(x-8)-1(x-8)=0$
$\Rightarrow(x-8)(8 x-1)=0$
$\Rightarrow x-8=0$ or $8 x-1=0$
$\Rightarrow x=8$ or $x=\frac{1}{8}$
∴ x = 8 (x is a natural number)
Hence, the required number is 8.