measurement

Question

The curved surface of a cylinder is 264m^2.Its volume is 924m^3. The height of the cylinder must be a 4m b 6m c 8m d none of these

killer1387 · Answer

romitvsingh wrote:The curved surface of a cylinder is 264m^2.Its volume is 924m^3. The height of the cylinder must be a 4m b 6m c 8m d none of these b 6M

rijul007 · Answer

Curved Surface area = 2πrh = 264 πrh =132 = 4*3*11 Volume = πr²h = 924 = 4*3*7*11 πrh*r = 924 r = 7 πrh = 132 3.14*7*h = 132 22h ≈ 132 h ≈ 132/22 h ≈ 6 IMO B

Brent@GMATPrepNow · Answer

romitvsingh wrote:The area of curved surface of a cylinder is 264m^2.Its volume is 924m^3. The height of the cylinder must be a 4m b 6m c 8m d none of these The area of the curved surface of a cylinder = 2(pi)rh So, if this area is 264, we can write 2(pi)rh = 264 Divide both sides by 2 to get (pi)rh = 132 The volume of a cylinder = (pi)(r^2)h So, if the volume is 924, we can write (pi)(r^2)h = 924 From here, we can "divide" the equations to get: (pi)(r^2)h/(pi)rh = 924/132 Simplify to get: r=7 Now that we know the value of r, we can plug this value into either equation to find the value of h. How about: (pi)(7)h = 132 This means that h = 132/7pi As you can see, h cannot be an integer, so the answer must be D. Cheers, Brent

romitvsingh · Answer

Brent@GMATPrepNow wrote:romitvsingh wrote:The area of curved surface of a cylinder is 264m^2.Its volume is 924m^3. The height of the cylinder must be a 4m b 6m c 8m d none of these The area of the curved surface of a cylinder = 2(pi)rh So, if this area is 264, we can write 2(pi)rh = 264 Divide both sides by 2 to get (pi)rh = 132 The volume of a cylinder = (pi)(r^2)h So, if the volume is 924, we can write (pi)(r^2)h = 924 From here, we can "divide" the equations to get: (pi)(r^2)h/(pi)rh = 924/132 Simplify to get: r=7 Now that we know the value of r, we can plug this value into either equation to find the value of h. How about: (pi)(7)h = 132 This means that h = 132/7pi As you can see, h cannot be an integer, so the answer must be D. Cheers, Brent your ans is wrong its b) 6

Brent@GMATPrepNow · Answer

romitvsingh wrote: your ans is wrong its b) 6

The height of the cylinder is 132/(7pi). This does not equal 6.
Sure, it's close to 6 (6.002414997etc), but it does not equal 6.

On the GMAT, the wording in the original question would never allow for 132/(7pi) to equal 6.

If we were to rewrite the original question to fit GMAT's sense of mathematical correctness, it would look something like this:

The area of the curved surface of a cylinder is 264, and its volume is 924. Which of the following is the best approximation of its height?
A) 4
B) 6
C) 8
D) 10
E) 12

Here, the word "approximation" allows for some wiggle room regarding the accuracy of the solution, the removal of the answer choice "none of these" eliminates ambiguity, and 5 answer choices (instead of 4) fits the GMAT standard.

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

ronnie1985 · Answer

simple calculations yield the result of 12 m

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