Question 287625
OK let us think our way thru this!
V=PI r^2 (height)

OK If we increase the radius and the volume stays the same, we have to decrease something on the other side. So something will be decreased. That leaves us B. C. and E. Now off to the races...
Pi r^2 H =Pi R^2 H
let us keep it simple! let r be 1 i.e. our initial radius.
pi (one) H= (now) pi (1.25)^2x   (x is our new height, see now how it has to be less than the other height?)

Let's get rid of the pi's they cancel out--how convenient!!!!
H=1.25^2x
H=25/16 (I changed 1.25 into 5/4 and squared this)x
divide both sides by 25/16
16/25H=x
Our new height is 16/25 of the original height. Original height was decreased by 9/25. (I am just working with the fractions here!) 9/25=.36 
ANSWER IS B.


Hint; Stick to the formula. Don't be afraid to let r be ONE to keep things simple! r^2 then is one.