Answer to Question 5

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Work out the decay constant:

 

l = 0.693 (1250 106 y 365 dy 86400s ) = 1.76 10-17 s-1

 

-lt = ln N - ln N0

 

-1.76 10-17 s-1 t = ln (500 106) - ln(608 106)

 

-1.76 10-17 s-1 t = -0.196

 

t = 1.1 1016 s (350 million years)