A) 1
B) 2
C) 3
D) 4
Correct Answer: C
Solution :
[c] Let \[a=100,\] \[(a-x)=80\] (Amount left). \[\therefore \] Amount left \[=\frac{a}{{{(2)}^{n}}}\] [n = number of half lives] \[80=\frac{100}{{{(2)}^{n}}}\Rightarrow {{(2)}^{n}}=\frac{10}{8}\] \[\therefore \,\,\,n\,\,\log 2=\log 10-3\log 2=1-3\times 0.3=0.1\] \[n=\frac{0.1}{\log 2}=\frac{0.1}{0.3}=\frac{1}{3}.\] AlternativelyYou need to login to perform this action.
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