XAT MOCK 3
Question 75
Data suffiency

If we take the three numbers to be a,ar&ar^2=27
ar=3
then using the second statement
ar^3+ar^4=36
3r+3r^2=36
r=3 or -4
if r was negative, 27 would be negative.

Then we can conclusively say that r is not negative as we have taken the other 3 numbers.