Question

The micro organisms in a culture increase by $20\%$ in the first hour, decrease by $10\%$ in the second hour and again increase by $20\%$ in the third hour. If the original count of micro organisms in a sample is $25000$, then find the bacteria count at the end of $3$ hours.

Answer 1

$Countofmicroorganism=25000$

$20\%increaseinfirsthour$

$so=25000\times \frac{120}{100}$

$10\%decreasein\sec ondhour$

$so=25000\times \frac{120}{100}\times \frac{90}{100}$

$20\%increaseinthirdhour$

$so=25000\times \frac{120}{100}\times \frac{90}{100}\times \frac{120}{100}$

$=32400$