A colony of bacteria starts with 900 organisms and double every 12 days

It follows that there will be:

how many organisms after 24 days....I assume 1800 right?

how many after 2 days

how should I approach it?

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- Aug 15th 2007, 06:00 PMTy DurdanAlgebra Word Problem
A colony of bacteria starts with 900 organisms and double every 12 days

It follows that there will be:

how many organisms after 24 days....I assume 1800 right?

how many after 2 days

how should I approach it? - Aug 15th 2007, 06:10 PMTKHunny
Doubles every 12 days. There is a standard exponential version, but sometimes I like just writing it down...

$\displaystyle 900*(2)^{Days/12}$

Test it.

$\displaystyle 900*(2)^{12/12} = 900*2^{1} = 900*2 = 1800$

Use it.

$\displaystyle 900*(2)^{24/12} = 900*2^{2} = 900*4 = 3600$ Oops. You had better check that.

Use it again.

$\displaystyle 900*(2)^{2/12} = ???$ - Aug 15th 2007, 06:24 PMTy Durdan
So would it be 75 organisms a day... because that would allow for 900 after 12 days, 1800 after 24 days...and 150 after 2 days.

- Aug 16th 2007, 06:01 AMTKHunny
You're guessing. Use the formula.

You START with 900. Why would there be only 900 still after 12 days?

Think about doubling.

Start: 900

12 days: 900*2 = 1800

24 days: 2*12 days = 900*2*2 = ??

Seriously, WRITE DOWN a working formulation. Don't try to do it in your head or on your calculator. Let the notation help you. Allow the algebra to soak into your brain and pour over your soul...:eek:

Ahem...Sorry, I got a little poetic, there. :rolleyes: - Aug 16th 2007, 06:14 AMtopsquark