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I have a relatively simple question. I'm just wondering, with half-life problems, how could I solve something like the following:

Isotope:226Ra

Half-life:1620 years.

Initial Quantity:X (Solve for this)

Amount after 1000 years:1.5g

Where I'm supposed to find the initial quantity.

Wouldn't a part of the equation be something like:.5 = e^1620r, whereris the rate of decay? I'm using natural log to try to get the rate:( ln(.5) / 1620 ) = r

When I punch that in to the calculator, I get huge number and it leads me to believe that I'm messing up somewhere.

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# Homework Help: Finding Half-Life

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