Discussion Forum

A positive number when decreased by 4 is equal to 21 times the reciprocal of the number. The number is :

Answer:

Explanation:

Let the numbers be $x$.
Then, $x-4=\frac{21}{x}$
$\Leftrightarrow x^{2}-4x-21=0$
$\Leftrightarrow (x+7)(x+3)=0$
$\Leftrightarrow x =7$.