college physics part 2
posted by Mimi .
the activity of a sample of carbon has oneeighth of the initial activity. carbon14 has a halflife of 5730 yr. how old is the sample in yr?

one eighth is three halflives.
Now the hard way:
amount left=original amount(1/2)^t/thalflife
1/8=(1/2)^t/th
t/th=3
or even harder:
amountleft=original*e^.693t/th
1/8=e^.693 t/th
ln of each side
ln (1/8)=.693 t/th
2.0793=.693 t/th
t/th= 3 
the question ask how old is the sample in yr. so that mean t/th is 3 yrs.