Last visit was: 13 Dec 2024, 09:32 It is currently 13 Dec 2024, 09:32
Close
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
Your Progress

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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
avatar
jhonnybravo
Joined: 28 Aug 2013
Last visit: 13 Nov 2013
Posts: 16
Own Kudos:
14
 []
Given Kudos: 3
Posts: 16
Kudos: 14
 []
Kudos
Add Kudos
7
Bookmarks
Bookmark this Post
User avatar
kusena
Joined: 14 Aug 2013
Last visit: 30 Dec 2014
Posts: 23
Own Kudos:
157
 []
Given Kudos: 4
Location: United States
Concentration: Finance, Strategy
GMAT Date: 10-31-2013
GPA: 3.2
WE:Consulting (Consumer Electronics)
Posts: 23
Kudos: 157
 []
2
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
sashiim20
Joined: 04 Dec 2015
Last visit: 05 Jun 2024
Posts: 620
Own Kudos:
1,682
 []
Given Kudos: 276
Location: India
Concentration: Technology, Strategy
WE:Information Technology (Consulting)
3
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
ScottTargetTestPrep
User avatar
Target Test Prep Representative
Joined: 14 Oct 2015
Last visit: 13 Dec 2024
Posts: 19,867
Own Kudos:
Given Kudos: 288
Status:Founder & CEO
Affiliations: Target Test Prep
Location: United States (CA)
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 19,867
Kudos: 24,280
Kudos
Add Kudos
Bookmarks
Bookmark this Post
jhonnybravo
A circular cloth with a diameter of 20 inches is placed on a circular tray with a diameter of 24 inches. What fraction of the tray's surface is NOT covered by the cloth?

A. 1/6
B. 1/5
C. 11/36
D. 25/36
E. 5/6

I have a silly question but I need some clarification why does it have to be the ratio of the area's and not circumference?

The area of the cloth is π x 10^2 = 100π, and the area of the tray is π x 12^2 = 144π. Therefore, 100π/144π = 100/144 = 25/36 of the tray’s surface is covered by the cloth. Thus, 1 - 25/36 = 11/36 of the tray’s surface is NOT covered by the cloth.

Answer: C
User avatar
CrackverbalGMAT
User avatar
GMAT Club Legend
Joined: 03 Oct 2013
Last visit: 13 Dec 2024
Posts: 4,878
Own Kudos:
Given Kudos: 224
Affiliations: CrackVerbal
Location: India
Posts: 4,878
Kudos: 8,145
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Radius of the tray =12 units

Area of the tray = pi * 12 *12 =144*pi

Radius of the cloth = 10 inches

Area of the cloth = pi * 10 * 10 =100*pi

Area of the tray's surface that is NOT covered by the cloth = 144*pi - 100*pi

=44*pi

Fraction of the tray's surface that is NOT covered by the cloth = 44*pi/144*pi

=11/36

(option c)

D.S
GMAT SME


User avatar
thesip2323
Joined: 08 Jul 2019
Last visit: 03 Dec 2022
Posts: 32
Own Kudos:
Given Kudos: 732
Posts: 32
Kudos: 5
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I can see I did not do the problem correctly but can someone tell me what my approach was trying to solve vs. what the correct approach was?

pi(12-10)^2 = 4pi which is the area not covered of the tray, so I got 4pi/144pi = 1/36, but I'm not too sure what is different about what I did vs. the approach others took to get 11/36.
User avatar
gmatchile
Joined: 26 Jan 2010
Last visit: 14 Nov 2023
Posts: 43
Own Kudos:
Given Kudos: 1
Status:casado
Location: chile
Concentration: Educación
WE 1: <!-- m --><a class="postlink" href=""></a><!-- m -->
WE 2: <!-- m --><a class="postlink" href=""></a><!-- m -->
WE 3: <!-- m --><a class="postlink" href=""></a><!-- m -->
Posts: 43
Kudos: 16
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Circular cloth diameter 20 inches
Round tray diameter 24 inches

Circular cloth radius 10 inches
Radius circular tray 12 inches

Circular cloth area 10exp2 x pi

Circular tray area 12exp2 x pi


Fraction of the tray not covered by the cloth:

(12exp2 x pi - 10exp2 x pi)/(12exp2 x pi)

Then:

(144 - 100)144
44/144
22/72
11/36

Answer C
Moderator:
Math Expert
97872 posts