Radioactive carbon decays exponentially with a half-life of 5,780 years. Determine how long ago a sample of carbon began to decay if there is now 5% of it left.

I'm not sure how to get started to all help is appreciated!

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- December 10th 2009, 08:14 PMAlice96Half-Life calculation
Radioactive carbon decays exponentially with a half-life of 5,780 years. Determine how long ago a sample of carbon began to decay if there is now 5% of it left.

I'm not sure how to get started to all help is appreciated! - December 10th 2009, 08:24 PMpickslides
Let A= the amount of radioactive material remaining at anytime t, you have the following information

Use the following

at and

this will help you solve for k.

After this solve for t when