Thursday

September 18, 2014

September 18, 2014

Posted by **Alex** on Thursday, January 13, 2011 at 11:22pm.

I know the equation is A=Ae^(-rt)

I tried working it out but I think I am doing it wrong.

I did 10=100e^(-r*2651)

Can anyone help? Thanks a lot

- Pre Calc -
**Reiny**, Friday, January 14, 2011 at 12:28amIf you want to use the e^kt function then you can find k the following way.

.5 = 1(e^2651k)

ln .5 = 2651k

k = ln.5/2651 = -.000261466

so we need:

10 = 100(e^ -.000261466t)

.1 = e^ -.000261466t

-.000261466t = ln .1

t = ln .1 / .000261466

t = 8806 years

or

Since you know you are dealing with half-life, we could use the equation

10 = 100 (.5)^(t/2651)

t/2651 = l .1 / ln .5

t = 8806

**Answer this Question**

**Related Questions**

calculus - The rate at which an amount of a radioactive substance decays is ...

Pre Calculus - Exponential growth and decay find the half life of a radioactive ...

AP Calculus - An Initial amount of 100 grams of Thorium-234 decays according to ...

Chemistry - Which radioactive sample would contain the greatest remaining mass ...

Physics HELP HELP - (for some reason I keep getting this wrong. I put 90 for c, ...

math - the half life of the carbon isotope C14 is about 5700 years. A. about how...

Math - _The_Natural_Base_e_ An accident in 1986 at the Chernobyl nuculear plant ...

calculus - Question: "Plutonium isotope Pu-239 has a half-life of 24,100 years. ...

Physics - Suppose you have 100 g of radioactive plutonium-239 with a half-life ...

Physics - Suppose you have 100 g of radioactive plutonium-239 with a half-life ...