Friday

April 18, 2014

April 18, 2014

Posted by **Anonymous** on Saturday, January 24, 2009 at 7:40pm.

1/2P = Pe^(-1690k)

(ln1/2)/(-1690) = k

4 x 10^-4 = k

5 = 50e^-kt

ln0.1 = -kt

ln0.1/-k = t

5,630 years = t

...but textbook answer is 5,614 years. Where did I go wrong?

- Math - Exponential Decay -
**Damon**, Saturday, January 24, 2009 at 7:51pmI got 5616 using 4.1 * 10^-4 for k

You did it right but did not carry the same number of significant figures.

it is easier to use a^-b = 1/a^b in a case like this

1/10 = e^-kt

becomes

e^kt = 10

t = ln 10/k = 2.303/.00041

- Math - Exponential Decay -
**bobpursley**, Saturday, January 24, 2009 at 7:53pmyour calculator. Set it on scientific, so the k is equal to 4.101E-4

With that, I get 5615 years.

- Math - Exponential Decay -
**DrBob222**, Saturday, January 24, 2009 at 7:57pmI, too, get 5615.

**Related Questions**

Chem 3A - please help me with this chemistry problem. Half-Life A radium-226 ...

Math - In 1976 a research hospital bought half a gram of radium for cancer ...

Math - In 1976 a research hospital bought half a gram of radium for cancer ...

chemistry - A radium-226 sample initially contains 0.112mol. How much radium-226...

Calculus - Radius decays at a rate of that is proportional to its mass, and has...

Pre Calculus - Radium-221 has a half-life of 30 s. How long will it take for 95...

Chemistry - Radium-223 has a half-life of 11.4 days.Approximately how long would...

Science - Radium has a half-life of 1620 years and decays into radon, which has...

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

Physics - A Geiger counter measures redioactive decay by registering the ...