Thread: Exponential Decay

A lab culture initially contains 500 bacteria. Two hours later, the number of bacteria has decreased to 200. Find the exponential decay model of the form

that can be used to approximate the number of bacteria after hours.

I have no idea where to start. Any ideas?

is the initial population at ... which is 500.

you were given another point on the curve ,

so, sub in 200 for B and 2 for t ... solve for k.

Originally Posted by skeeter

is the initial population at ... which is 500.

you were given another point on the curve ,

so, sub in 200 for B and 2 for t ... solve for k.

What would you sub in for a though?

Cause when I substitute what you said, I get the equation and when I solve for , I get . What would a be?

"a" can be any positive value you want that doesn't equal 1.

I'd use "e" since it's calculator friendly.

Originally Posted by skeeter

"a" can be any positive value you want that doesn't equal 1.

I'd use "e" since it's calculator friendly.

Ok thanks alot. I finally got it.

Originally Posted by chrozer

Ok thanks alot. I finally got it.

What is the final answer? -.458?

I'd use "e" since it's calculator friendly.

____________________
Purchase the most fantastic series and The Bible DVD canada with high qaulity for free home delivery!