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a) Half-life is the taken for a given mass of radioactive isotope to reduce to half
b) No. of half lifes = $\frac{100}{25}$ = 4
therefore $\frac{5}{M}$ = ($\frac{1}{2}$)4 $\rightarrow$ M = 80g
johnmulu answered the question on February 22, 2017 at 05:35
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