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Q.
$3$ numbers are in GP therefore, their logarithms are in
ManipalManipal 2013
Solution:
$a, b, c$ are in $G P \Rightarrow b^{2}=a c$
taking log on both the sides, we get
$2 \log b=\log a+\log c$
$\Rightarrow \log b=\frac{\log a+\log c}{2}$
$\Rightarrow \log a, \log b, \log c$ are in $AP$.