``If 18g of a radioactive substance are present initially and 5 yr later only 9 g remain, how much of the substance will be present after 11yr ?

Question

after 11yr there will be ___g of a radioactive substance.
round the final answer to the nearest thousandth as needed. round all intermediate values to the nearest thousandth as needed.''

Answer 1

half life is 5 years

amount remaining= 18*e^(-.692*11/5)
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18*e^(-.692*11/5)=