Question

A $50$ ml after-shave lotion at $30\%$ alcohol is mixed with $30$ ml of pure water. What is the percentage of alcohol in the new solution?

• A. $18.75$%
• B. $28.75$%
• C. $38.75$%
• D. $48.75$%

Answer 1

The correct option is A $18.75$%

The amount of the final mixture is given by,

$\Rightarrow$ $50ml+30ml=80ml$

The amount of alcohol is equal to the amount of alcohol in pure water plus the amount of alcohol in the $30\%$ solution.

Let $x$ be the percentage of alcohol in the final solution.

$\therefore$ $0+30\%of50=x\left(80\right)$

$\Rightarrow$ $\frac{30}{100}\times 50=80x$

$\Rightarrow$ $15=80x$

$\Rightarrow$ $x=\frac{15}{80}$

$\therefore$ $x=0.1875$

$\Rightarrow$ $x=0.1875\times 100=18.75\%$