GRE Prep 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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
If a right circular cylinder’s radius is halved and its heig
[#permalink]
19 Sep 2018, 17:52
19 Sep 2018, 17:52
Expert Reply
1
Bookmarks
00:00
Question Stats:
64% (01:01) correct
35% (01:03) wrong based on 48 sessions
Hide Show timer Statistics
If a right circular cylinder’s radius is halved and its height doubled, by what percent will the volume increase or decrease?
(A) 50% decrease
(B) 0%
(C) 25% increase
(D) 50% increase
(E) 100% increase
(A) 50% decrease
(B) 0%
(C) 25% increase
(D) 50% increase
(E) 100% increase
Re: If a right circular cylinder’s radius is halved and its heig
[#permalink]
15 Apr 2020, 06:15
15 Apr 2020, 06:15
1
sandy wrote:
If a right circular cylinder’s radius is halved and its height doubled, by what percent will the volume increase or decrease?
(A) 50% decrease
(B) 0%
(C) 25% increase
(D) 50% increase
(E) 100% increase
(A) 50% decrease
(B) 0%
(C) 25% increase
(D) 50% increase
(E) 100% increase
Volume of a circular cylinder = \(\pi\) * \({radius}^2\) * height
now, when the radius is reduced by 2 and height doubled, volume = \(\pi * {\frac{R}{2}}^2 * 2H\)= \(\frac{{\pi * {R}^2 * H}}{2} \), which is decreased by 50%
*****We can use some nice nos.
Let Radius = 4
Height = 2
Volume =\( \pi*4^2 * 2 = 32\pi\)
Radius is halved and height doubled, volume =\( \pi*2^2 * 4 = 16\pi\) , i.e volume decreased by 50%
Re: If a right circular cylinder’s radius is halved and its heig
[#permalink]
11 May 2020, 03:39
11 May 2020, 03:39
Using Numbers
let r = 4 and h = 2
Volume = pi.16.2 = 32.pi
Now, r = 2 and h = 4, since radius is halved and height is doubled. We get,
New Volume = pi.4.4 = 16.pi
We see that the new volume is half that of the old volume so the volume decreases by 50%, Answer is A.
Using Formulas
Old Volume = pi.r.r.h
New Volume = pi.(r/2).(r/2).2h
= (pi.r.r.2.h)/4
= (pi.r.r.h)/2
New Volume is half that of the Old Volume, therefore there is a 50% decrease in volume, Answer is A.
let r = 4 and h = 2
Volume = pi.16.2 = 32.pi
Now, r = 2 and h = 4, since radius is halved and height is doubled. We get,
New Volume = pi.4.4 = 16.pi
We see that the new volume is half that of the old volume so the volume decreases by 50%, Answer is A.
Using Formulas
Old Volume = pi.r.r.h
New Volume = pi.(r/2).(r/2).2h
= (pi.r.r.2.h)/4
= (pi.r.r.h)/2
New Volume is half that of the Old Volume, therefore there is a 50% decrease in volume, Answer is A.
