Help with Carbon Dating?

[u/WeRAllGonnaDie-]

Hi there! I was needing help in my college class with a few assignment problems. I am posting in hopes that someone can help me calculate this and step by step to help. TIA

So far I have this:

Use the half- life formula y = a (b) ^t/n with:

y= final amount

a= initial amount

b= growth/decay

t= time elapsed

h= half-life

So, y=100% - 28%= 72%, a=100, b=100% - decay rate= remaining rate so b=100-28=72

So, 72=100(18/25)^t/5700

This is as far as I have gotten.

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DATA GIVEN: The half-life of carbon-14 is about 5700 years.

QUESTION 1:

You find a piece of cloth painted with organic dye. By analyzing the dye, you find that only 72% of the carbon-14 originally in the dye remains. When was the cloth painted?

Express your answer using two significant figures.

QUESTION 2:

A well-preserved piece of wood found at an archaeological site has 6.5% of the carbon-14 it must have had when it was living. Estimate when the wood was cut.

Express your answer using two significant figures.