# Math Help - Algebra Word Problem

1. ## Algebra 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?

2. Originally Posted by Ty Durdan
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?
Doubles every 12 days. There is a standard exponential version, but sometimes I like just writing it down...

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

Test it.

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

Use it.

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

Use it again.

$900*(2)^{2/12} = ???$

3. 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.

4. You're guessing. Use the formula.

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

Start: 900
12 days: 900*2 = 1800
24 days: 2*12 days = 900*2*2 = ??

$900*(2)^{Days/12}$
$900*(2)^{2/12} \approx 1010.22$