Question

A colony of bacteria triples in link every 10 minutes. It's length is now 1 mm. How long will be in 40 minutes

Answer 1

If the bacteria is tripling every 10 minutes, that means the "rate of increase" on that period is 200%, so if say the current amount is "c", 200% of "c" is just 2c, so c + 2c is 3c, a tripled amount.

$\bf \textit{Periodic Exponential Growth}\\\\ A=I(1 + r)^{\frac{t}{p}}\qquad \begin{cases} A=\textit{accumulated amount}\\ I=\textit{initial amount}\to &1\\ r=rate\to 2\%\to \frac{200}{100}\to &2.00\\ t=\textit{elapsed time}\to &40\\ p=period\to &10 \end{cases} \\\\\\ A=1(1 + 2)^{\frac{40}{10}}$