A certain element decays at a constant rate of 3% per year.If you start with 15 grams of the element, how long will it take before there are only three grams left?
Question
A certain element decays at a constant rate of 3% per year.If you start with 15 grams of the element, how long will it take before there are only three grams left?
Solution
To solve this problem, we can use the formula for exponential decay, which is:
N = N0 * e^(rt)
where: N is the final amount of the substance, N0 is the initial amount of the substance, r is the decay rate, and t is the time.
In this case, we know that N = 3 grams, N0 = 15 grams, and r = -0.03 (since it's a decay rate of 3% per year). We want to find t.
So we can set up the equation as follows:
3 = 15 * e^(-0.03t)
To solve for t, we first divide both sides by 15:
3/15 = e^(-0.03t)
0.2 = e^(-0.03t)
Then we take the natural logarithm (ln) of both sides:
ln(0.2) = ln(e^(-0.03t))
ln(0.2) = -0.03t
Finally, we solve for t by dividing both sides by -0.03:
t = ln(0.2) / -0.03
Using a calculator, we find that t ≈ 61.1 years.
So it will take approximately 61.1 years for the element to decay from 15 grams to 3 grams.
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