Respuesta :

marmal
[tex]M=m_o*\frac{1}{2}^\frac{t}{T}\\ M-mass\ aftter\ decay\\ m-initial\ mass\\ t-time\\ T-period(half-life)\\ 25=200*\frac{1}{2}^\frac{3460}{T}|:200\\ \frac{1}{8}=(\frac{1}{2})^\frac{3460}{T}\\ (\frac{1}{2})^3=(\frac{1}{2})^\frac{3460}{T}\\ 3=\frac{3460}{T}\\ T=1153\frac{1}{3}[/tex]

or easiest way
200g ----->  100g -------> 50g -----> 25g
We can that there were three decays.
1 decay ----------- x years
3 decays---------- 3460
[tex]x=1153\frac{1}{3}[/tex]

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