The surface area of cylinder A is how many times the surface area of

Question

The surface area of cylinder A is how many times the surface area of cylinder B?

(1) The diameter of A is twice the diameter of B.
(2) The height of A is equal to the height of B.

Another challenging geometry question.

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divyadna · Answer

The surface area of cylinder A is how many times the surface area of cylinder B?

(1) The diameter of A is twice the diameter of B.

SA of cylinder= 2πrh+2πr^2= 2πr(h+r)
SA of A:SA of B= 2π.2r (h+2r)/2πr(h+r)

Statement I is clearly insufficient.
Reject A and D.

(2) The height of A is equal to the height of B.
SA of cylinder= 2πrh+2πr^2= 2πr(h+r)
SA of A:SA of B= 2πR(h+R)/2πr(h+r)

Again, statement II is insufficient.

Combining the two statements 
SA of cylinder= 2πrh+2πr^2= 2πr(h+r)
SA of A:SA of B= 2π*2r(h+2r)/2πr(h+r)= 2(h+2r)/(h+r)

Statement I and Statement II together are insufficient.

Ans is option E

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Maria240895chile · Answer

Area of a cylinder is the sum of the areas of all its surfaces 2 times area of the base+area of rectangle= 2*(2πr) + 2πr*h

(I) we do not know the height of neither cylinder. INSUFFICINET
(II)we know the height but not the diameter of both cylinder. INSUFFICENT

(I)y(II) since they are asking  how many times  is A from B we can assign a value for B radius, let's say is 2, and we know by (I) that diameter of A is twice the diameter of B so should be 4. Based on 2 we know they have the same height so lets call it 10.

so area of A = 2(2π4)+2π4*10= 16π+80π=96π
area of B =2(2π2)+2π2*10=8π+40π=48π

now a/b=96π/48π= 2

so area of A is twice the area of B

IMO C

gmatophobia · Answer

Total Surface Area of a Cylinder =  2 * \pi * r^2 + 2 * \pi * r * h 
=  2 \pi r (r + h)

Statement 1 and Statement 2 are individually not sufficient as only one aspect of the dimension is provided.

Combined

Cylinder A  : 
  Radius = 2r 
 Height = h

Cylinder B: 
  Radius = r 
 Height = h

\frac{TSA_A }{ TSA_B} = \frac{2 \pi *2r (2r + h) }{ 2 \pi r (r + h)}

\frac{TSA_A }{ TSA_B} = \frac{2(2r + h) }{ (r + h)}

As we cannot solve this further. The statements combined are not sufficient.

Option E

The surface area of cylinder A is how many times the surface area of

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GMAT Data Sufficiency (DS) Questions

The surface area of cylinder A is how many times the surface area of

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