GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 19 Oct 2018, 23:45

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# If the same amount of material is used to make a hollow cylinder and a

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50002
If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

17 Sep 2018, 22:05
00:00

Difficulty:

85% (hard)

Question Stats:

42% (01:39) correct 58% (01:57) wrong based on 76 sessions

### HideShow timer Statistics

If the same amount of material is used to make a hollow cylinder and a hollow cube, which one of the two will have a greater height?

(1) The perimeter of the base of the cube is larger than the circumference of the base of the cylinder.
(2) The volume enclosed by the cylinder is 30π.

_________________
Manager
Joined: 21 Jun 2017
Posts: 86
Concentration: Finance, Economics
WE: Corporate Finance (Commercial Banking)
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

26 Sep 2018, 21:12
A
given : a^3 = pi*r^2*h or (a^3/pi*h)^1/2 = r. Asked = To comment on ratio of a/h

statement 1 Sufficient. -----4a>2pi*r ----- After deuducing, --- h/a > Pi*4
Statement 2 Insufficient.

Where have i gone wrong
_________________

Even if it takes me 30 attempts, I am determined enough to score 740+ in my 31st attempt. This is it, this is what I have been waiting for, now is the time to get up and fight, for my life is 100% my responsibility.

Manager
Joined: 21 Jun 2017
Posts: 86
Concentration: Finance, Economics
WE: Corporate Finance (Commercial Banking)
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

27 Sep 2018, 21:41
chetan2u

Hi !!! your two cents on this one sir

Regards
_________________

Even if it takes me 30 attempts, I am determined enough to score 740+ in my 31st attempt. This is it, this is what I have been waiting for, now is the time to get up and fight, for my life is 100% my responsibility.

Math Expert
Joined: 02 Aug 2009
Posts: 6961
If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

27 Sep 2018, 23:07
1
Bunuel wrote:
If the same amount of material is used to make a hollow cylinder and a hollow cube, which one of the two will have a greater height?

(1) The perimeter of the base of the cube is larger than the circumference of the base of the cylinder.
(2) The volume enclosed by the cylinder is 30π.

Hi..

Shank18, you have gone wrong in assuming that material means volume..
Yes, it would be correct of the elements were solid, here they are hollow..

So volume of material use will equal to SURFACE AREA*THICKNESS of each item..
So $$t_1*2πrh=t_2*6l^2$$
We have to find l:h

(1) The perimeter of the base of the cube is larger than the circumference of the base of the cylinder.
$$4l>2πr.....2l>πr$$
Insufficient

(2) The volume enclosed by the cylinder is 30π
$$πr^2h=30π......r^2h=30$$
Not sufficient information given

Combined..
We do not the ratio of $$t_1$$ and $$t_2$$, the thickness of each..
Insufficient

E
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Manager
Joined: 21 Jun 2017
Posts: 86
Concentration: Finance, Economics
WE: Corporate Finance (Commercial Banking)
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

27 Sep 2018, 23:57
Agree with the explanation. But, shouldn't the thickness be negligible to consider since it's hollow ?

Btw sir , you have explained this wonderfully well...Thanks

Posted from my mobile device
_________________

Even if it takes me 30 attempts, I am determined enough to score 740+ in my 31st attempt. This is it, this is what I have been waiting for, now is the time to get up and fight, for my life is 100% my responsibility.

Intern
Joined: 08 Feb 2018
Posts: 5
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

29 Sep 2018, 11:37
chetan2u
hello, could you please explain why you took (2 pi r h) = surface area of the budy of cylinder with out the two bases?
and why you took (6 l^2) not (4 L *6) ?
thanks
Math Expert
Joined: 02 Aug 2009
Posts: 6961
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

29 Sep 2018, 20:41
1
Qusay wrote:
chetan2u
hello, could you please explain why you took (2 pi r h) = surface area of the budy of cylinder with out the two bases?
and why you took (6 l^2) not (4 L *6) ?
thanks

Hi..
It is not given if base and top are there, so you could take that also, but the main point is that there is nothing about thickness, so you can't find the answer..
Surface area of cube will be (6 faces*areaa of each face)=(6*L^2)

Shank18,
Hollow just means it is not solid but you cannot take the thickness to be 0..
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Manager
Joined: 01 Jan 2018
Posts: 62
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

29 Sep 2018, 23:09
1
Hi Chetan2u,
Shouldn't the statement 1 be--4l>2πr(since perimeter of base of cube will be 4l) and not

(1) The perimeter of the base of the cube is larger than the circumference of the base of the cylinder.
2l>2πr.....l>πr
_________________

+1 Kudos if you find this post helpful

Math Expert
Joined: 02 Aug 2009
Posts: 6961
Re: If the same amount of material is used to make a hollow cylinder and a  [#permalink]

### Show Tags

30 Sep 2018, 00:10
dvishal387 wrote:
Hi Chetan2u,
Shouldn't the statement 1 be--4l>2πr(since perimeter of base of cube will be 4l) and not

(1) The perimeter of the base of the cube is larger than the circumference of the base of the cylinder.
2l>2πr.....l>πr

dvishal387,
Yes you are correct. I was not interested in other values as not knowing thickness was not helping us
Thanks
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Re: If the same amount of material is used to make a hollow cylinder and a &nbs [#permalink] 30 Sep 2018, 00:10
Display posts from previous: Sort by