15/x = 5/11
5x = 165
x = 33
In general, the volume

has total derivative

If the cylinder's height is kept constant, then

and we have

which is to say,

and

are directly proportional by a factor equivalent to the lateral surface area of the cylinder (

).
Meanwhile, if the cylinder's radius is kept fixed, then

since

. In other words,

and

are directly proportional by a factor of the surface area of the cylinder's circular face (

).
Finally, the general case (

and

not constant), you can see from the total derivative that

is affected by both

and

in combination.
Answer:
D
Cost per person × number of persons = total cost
29.50 × 3 = x
Answer:
The perimeter of this triangle should be 34 units.