Question

In a culture, the present bacteria count was found as $67,60,000$. It was found that the number was increased by $4\%$ per hour. Find the number of hours before which the bacteria count was $62,50,000$.

• A. $1$ hr
• B. $2$ hr
• C. $3$ hr
• D. $4$ hr

Answer 1

The correct option is B $2$ hr

Let the number of years be $n$

$\Rightarrow 67,60,000=62,50,000{[1+\frac{4}{100}]}^n$

$\Rightarrow \frac{676}{625}=[1+\frac{1}{25}{]}^n$

$\Rightarrow {\left[\frac{26}{25}\right]}^2={\left[\frac{26}{25}\right]}^n$

$n=2$ hrs

Thus, the number of hours are $2$.