Aptitude - Volume and Surface Area - Discussion

Formula:
curved surface area(CSA) of a cylinder = 2πrh.
Volume(V) of a cylinder = π*r*r*h.
Given :
CSA = 264 .
V = 924.
Solution :
CSA = 2πrh = 264.
V = π*r*r*h = 924.
To find r, let us divided volume by CSA.
π*r*r*h/2πrh = 924/264.
After cancelling π, h, r, we get,
r = 2 * (924/264),
So, r = 7.
Subsitute value of r in 2πrh to find the value of h.
2πrh = 264 (given)
2 * 3.14 * 7 * h = 264.
On solving h = 6.
Now, diameter = 2 * r.
Diameter = 2 * 7 = 14.
Height = 6.
Ratio is 14/6 = 14 : 6 = 7 : 3.

@Goki.

we know radius =diameter/2,so diameter d =2r.

Not understanding, Please someone explain me.

@Goki.

It is simple, see we have to find the ratio of its diameter to its height right and diameter is = 2r.

What step is taken after first step anyone help me?

Why we are taking 2R?

The C.S.A of the cylinder is 2φRH.
The volume of a cylinder is φ * r * r * h.

We have to find diameter/height.

So, if we divide them i.e CSA/Volume, This would give us the value of Radius.

=> φ * r * r * h/2 * φ * r * h = 924/264 = 7.
R = 7m.
Now we have to find H.
For H, Take 2*φ * r * h = 264.

Substitute the value of R in CSA(curved surface area),
The value of H is 6.
So, 2r /h = 7/3.

I didn't get this. Anyone explain this sum clearly?

Required ratio = 2r = 14 = 7:3.

How can you write 2r divided by h? h=6.

Given:

Surface area of cylinder(s.a) 2*pi*r*h = 264.
Volume of the cylinder(v) pi*r*r*h = 924.

In order to find radius calculate s.a/v or v/s.a which gives the radius value as 7 m.

In order to find height take s.a formula or v formula and substitute the required values to get the height value.