32% of a particular radioactive substance disappears in 227 years.

Part 1: Find the decay constant. Your answer must be correct to five decimal places.
Part 2: Determine the time T in years required for 93% of the substance to disapper. Your answer must be correct to two decimal places
WARNING: Do not round off values during calculations.

we know that the fraction remaining after t years is f(t)=e^-(kt) for some k.

So, find k:

f(227) = e^(-227k) = 0.68
k = 0.001699
So,

f(t) = e^(-.001699t)

I expect you can take it from here, ok?