Question

The ratio of number of elephants now and 5 years ago is $1:2$. The percentage decrease in the number of elephants over these years is %.

• A. $30$
• B. $40$
• C. $50$
• D. $60$

Answer 1

The correct option is C $50$

Given ratio is $1:2$
Let the common ratio to be x.
∴ Initial value = $2x$ and
Final value = $x$


$\because \%increase=\frac{Finalvalue-Initialvalue}{InitialValue}\times 100\%$

Putting the values, you get,
$\%increase=\frac{x-2x}{2x}\times 100\%$
$=\frac{-x}{2x}\times 100\%$
$=-50\%$

As the increase in percentage is negative,
so, the percentage decrease in the number of elephants will be $50\%$.