a reaction is first order and it takes 324 minutes for the reaction to be 50% complete. How long will it take for the reaction to be 85% complete at the same temperature?

Answer 1

ln(No/N) = kt
ln(100/50) = k*324.
Solve for k, then substitute back into
ln(100/15) = k*t and solve for t.

Answer 2

it says the answer is 887 minutes. am i doing something wrong . when i use that formula i don't get 887