Question

A man says, “I am thinking of a number. When I divide it by 3 and then add 5, my answer is twice the number I thought of”. Find the number.

Answer 1

Let the required number be x. So, according to the question:
$\Rightarrow \frac{x}{3}+5=2x$
$\Rightarrow 5=2x–\left(\frac{x}{3}\right)$
$\Rightarrow 5=\frac{(6x–x)}{3}$
$\Rightarrow 5=\left(\frac{5x}{3}\right)$
Multiplying both sides by 3 we get,
$\Rightarrow 5\times 3=\left(\frac{5x}{3}\right)\times 3$
$\Rightarrow 15=5x$
Dividing both sides by 5 we get
$\Rightarrow \frac{15}{5}=\frac{5x}{5}$
$\Rightarrow 3=x$
Thus the number thought of by the man is 3.