# TO ANY SCIENCE HELPER

Like say my question was a sample has 80% of its original carbon-14 present. How do I determine the age of the sample?

Like I don't get how to get the answer, this concept is very difficult for me

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1. You know the half life for carbon 14 is 5,730 years. If you aren't told that in the problem you can look it up. You can calculate the rate constant (which you will need later) this way.
k = 0.693/t1/2
k = 0.693/5730 = 1.21E-4
Substitute this k into the equation below.
ln(No/N) = kt.
No = what you started with.
N = what yu end up with
k = from above
t = years it took to go from No to N.
They don't give you a number for No so you choose a convenient one to use. It makes no difference what number you choose but I suggest 100.
No = 100
N = the problem says it has 80% of it's original. So since we picked 100, then 100 x 0.80 = 80 (now you know why I picked 100). If you chose any other number then it's the number you chose x 0.80. So
N = 80
k = from above. solve for t
ln(100/80) = 1.21E-4*t and solve for t. I won't go through the steps here (this is where a blackboard would come in handy) but when I do the math I get 1844 years if I did the math right. Post any follow up questions here.

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2. Ok, I kinda understand it now. Thank u so much :)

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