Algebra Problem Help Needed

[mlwilliamsiv]

Hey Guys...

I've been racking my brain trying to figure this problem out:

The number of bacteria in a certain population increases according to an exponential growth model, with a growth rate of 4% per hour. How many hours does it take for the size of the sample to double? Round your answer to two decimal places.

I've been searching on google for some formulas to help me but I just can't seem to get it... I figure since the problem doesn't tell me how many bacteria there are then I could just pick a number like 100. I'm just not good with formulas and word problems.

Any help would be greatly appreciated thanks...

From a loyal degree seeker,

[NAP]

Hi!

Have you seen these sites?

Rate of growth equation help? - Yahoo! Answers

Exponential Growth and Decay

They look promising.

I hope this helps!

[mlwilliamsiv]

Thanks NAP

[ideafx]

I believe the answer is 17.33 hours, but please double check my work.

The formula you want is A = Pe^rt

There's more information about it here: Exponential Word Problems

A = Pe^rt
2 = e^.04t
ln(2) = .04t*ln(e)
0.693 = .04t
17.33 = t