Using differential equations to determine the decay constant for carbon-14

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Homework Statement


Q(t) is the amount of carbon 14 at time t. Given half life of 5730 years, and assuming that Q satisfies dQ/dt=-rQ; determine decay constant r


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The Attempt at a Solution


I solved the differential equation and got Q=ce^-rt. Now what? And hints/help?
 
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The half life is 5730 years, that means that Q(5730)=(1/2)Q(0)
 
thanks i figured it out
 
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