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## Homework Statement

The half-life of a radioactive substance is 3200 years. Find the quantity Q(t) of the substance left at time t>0 if Q(0)=20 g.

## Homework Equations

dQ/dt=kQ

## The Attempt at a Solution

dQ/dt=kQ

dQ/Q=k dt

ln abs(Q)=kt+C

Q=Ce^(kt)

C=20

Q=20e^(kt)

20e^(3200k)=10

e^(3200k)=1/2

Now I'm stucked. The answer is Q=20e^(-(t*ln2)/3200) g.