Calculate Age Based on Radioactive Decay

[Wictorian]

Do you know what the formula is? I have done some research but it is very counter intuitive for me.

[Ryuikko]

 Radioactive decay is an exponentioal decay so If you're given the half life of the substance, and the amount it was after (t) time, then you just solve it like any other exponential problem. 

[Isuck Assimov]

https://en.wikipedia.org/wiki/Radiocarbon_dating

[Wictorian]

19 minutes ago, Ryuikko said:

 Radioactive decay is an exponentioal decay so If you're given the half life of the substance, and the amount it was after (t) time, then you just solve it like any other exponential problem. 

The thing is I don’t know how to solve exponential problems.

[Ryuikko]

15 minutes ago, Wictorian said:

The thing is I don’t know how to solve exponential problems.

So for example, if I was given that a substance has a half life of 350 years  and it has retained 64% of its original amount, I'd write the equation being something like this

 

Expected amount=initial(1/2)^t/half life

So written out would be 

64=100(1/2)^t/350

Your initial being 100% since that's the whole, and you can express percentages as out of 100, so 64% of 100 would be 64

Divide both sides by 100 to get the function by itself

64/100=(1/2)^t/350

.64=(1/2)^t/350 

You can then log both sides, and by the power rule you can move t/350 to the front such as

Log(.64)=t/350×log(1/2 or .5)

Then divide log(1/2) from both sides to get

Log(.64)/log(.5)=t/350

Then you can multiply each side by 350 so you can have

Log(.64)/Log(.5) × 350 = t

t(in years is =225.35)