Question 72205
Find the missing geometric sequence 15, __ , 81,...
Show work 
If it's a geometric sequence there must be a "common ratio" "r" between
the terms.
So the terms are 15, 15r,(15r)r
Thus 15r^2=81
r^2=81/15
r=9/sqrt15
So the missing element is 15(9/sqrt15) = 9sqrt15
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Find the missing geometric sequence 36, __ , 100, ... 
Following the same argument as above:
36r^2=100
r^2=100/36
r=10/6 = 5/3
Therefore the missing term is 36(5/3)=60
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Cheers,
Stan H.