1. ## half life problem

I have this problem:
The half-life of radium is 1690 years. How much will be left of 32 grams of radium after 6760 years?
I know to use the formula:
y = Ce^(kx) Where C is the original amount, y is the future amount, k is rate, and x is time. I am having some trouble figuring out what pieces go where. I am thinking the 1690 years is the x, but I'm not so sure of the rest. Also..this is off topic, but is it fine that I am asking a lot (maybe too many in some opinions) questions? I have been strugling with calc 2 since I started it monday. The class is Mon-Fri, 2 hours each day. This is a good way for me to learn..by practicing and finding out what I am doing right/wrong to improve my skills. Thanks everyone.

2. The decay constant k is $\frac{-1}{T}ln(2)=\frac{-1}{1690}ln(2)\approx{-0.00041014626...}$

At t=0 there is 32 grams, so that $y(6760)=32e^{-0.00041014626(6760)}= 2 \;\ grams$

3. Originally Posted by galactus
The decay constant k is $\frac{-1}{T}ln(2)=\frac{-1}{1690}ln(2)\approx{-0.00041014626...}$

At t=0 there is 32 grams, so that $y(6760)=32e^{-0.00041014626(6760)}= 2 \;\ grams$
How did you find the decay constant?

4. By the formula I gave you.

$k=\frac{-1}{T}ln(2)$.

That comes from halving time being given by $T=\frac{-1}{k}ln(2)$