**8/26/2014
****If
three numbers log ***a***,
log ***b***,
log ***c***
****from
an arithmetic progression (in that order), which of the following is
true?**

a) *b *= *ac*

b) *c* = *ab*

c) *b* = (*a *+ *c*)/2

d) *b*^{2} = *ac*

e) *b*^{2} = *a *+
*c*

**Scroll
down for the solution.**

**8/26/2014
**Solution.
**D.
**Since
**log
***a***,
log ***b***,
log ***c***
****from
an arithmetic progression, log ***b
– ***log
***a
***=
log ***c
–***
****log
***b***
****[since
they form the same common difference], so that log (***b
***/****
***a***)
= log (***c
***/***b***)
→ ***b*^{2}**
****=
***ac
***after
canceling the ***log
***and
cross-multiplying***.*