SOLUTION: A radioactive substance has a halflife of 120 years. If 200mg of substance was present, how much of the substance remains after 340 years?

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Question 841313: A radioactive substance has a halflife of 120 years. If 200mg of substance was present, how much of the substance remains after 340 years?
Answer by ewatrrr(24785) About Me  (Show Source):
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Hi,

A radioactive substance has a halflife of 120 years

Q%28t%29+=Q%5B0%5De%5E%28-kt%29  

   +.5+=+e%5E%28-k%2A120%29

      ln(.5)/-120 = k = .0058

Q%28340%29+=%28200mg%29e%5E%28-.0058%2A340%29