Discussion Forum



1)

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


A) 3

B) 5

C) 7

D) 9

E) 10

Answer:

Option C

Explanation:

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