Answer:
Two figures are similar if the figures have the same shape but different sizes.
Then if we have two figures X and X'
Such that one dimension of X is D, the correspondent dimension on X' will be:
D' = k*D
Such that k is the scale factor that relates the figures.
1:k
Because all the dimensions will be rescaled by the same scale factor k, we can conclude that any surface on X will be related to the same surface in X' by:
S' = k^2*S
then the ratio of the surfaces is:
1:k^2
While the relation between the volumes will be:
V' = k^3*V
Here the ratio is:
1:k^3
Ok, in this case we have two cylinders
We know that the ratio between the base area ( a surface) is:
9:25
a) We want to find the ratio: curved surface area of A : curved surface area of B
Because again we have a surface area, the ratio should be exactly the same as before, 9:25
b) height of A : height of B
In this case, we have a single dimension.
Because in the rescaling of a surface we need to use k^2, then we can conclude that the ratios:
9:25
is related to k^2
Then the ratio, in this case, is given by applying the square root to both sides of the previous ratio, so we get:
√9:√25
3:5
This is the ratio of the heights.
Also from this we could get the value of k, that is the right value when we leave the left value equal to 1, we can get that if we divide both sides by 3.
(3/3):(5/3)
1:(5/3)
Then:
k = 5/3
becomes 
and 4 
becomes 
. Now we have to find a LCD. An LCD for 4 and 8 is 8, so now we have to change 
when you multiply the fraction by the form of 1 
. 34 + 43 = 77, so our answer is 77/8 which simplifies to 9 
.