Question

The square of a positive number exceeds three times that number by $180$. Find the number.

• A. $15$
• B. $14$
• C. $13$
• D. $12$

Answer 1

Answer: (A)

$15$

If the required number is $x$, then $x^2-3x=180$
$\Rightarrow x^2-3x-180=0$

$\Rightarrow x^2-15x+12x-180=0$

$\Rightarrow x(x-15)+12(x-15)=0$
$\Rightarrow (x-15)(x+12)=0$
Thus $x=15$

As, $x$ $=$ $-12$ does not apply because the number given is positive, so the number is $15$.