December 11, 2018 December 11, 2018 09:00 PM EST 10:00 PM EST Strategies and techniques for approaching featured GMAT topics. December 11 at 9 PM EST. December 13, 2018 December 13, 2018 08:00 AM PST 09:00 AM PST What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.
Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 04 Aug 2010
Posts: 6

In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
Updated on: 13 Feb 2015, 07:20
Question Stats:
63% (02:52) correct 37% (02:44) wrong based on 146 sessions
HideShow timer Statistics
In a shop, 40% socks are white and rest are black. 60% socks are made of cotton and rest are made of wool. 25% white socks are made of cotton and 20 of the black socks are made of wool. How many black socks are made of cotton? A) 100 B) 80 C) 60 D) 50 E) 25
Official Answer and Stats are available only to registered users. Register/ Login.
Originally posted by newmoon on 16 Sep 2011, 08:10.
Last edited by Bunuel on 13 Feb 2015, 07:20, edited 1 time in total.
Renamed the topic and edited the question.




Manager
Joined: 04 Jun 2011
Posts: 156

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
16 Sep 2011, 08:48
newmoon wrote: Please elaborate the solving method.
In a shop, 40% socks are white & rest are black. 60% socks are made of cotton & rest are made of wool. 25% white socks are made of cotton & 20 of the black socks are made of wool. how many are black socks are made of cotton? A)100 B)80 C)60 D)50 E)25 ok here u go.... lets say total number of socks = x 40% is white > wht = 0.4x Blk = 0.6 x also 60% socks are made of cotton  > ct = 0.6x wl = 0.4x we know 25% of the white socks is cotton > 1/4 (0.4x) = 0.1x = whct => 0.3x = whwl total wool is 0.4x => black wool socks = 0.4 x (total)  0.3 x (whwl) = 0.1x given as 20 => total number of socks = 200 = > total black socks = .6x = 120 total cotto black socks = 120  20 (blwl) = 100 hence A




Senior Manager
Joined: 11 May 2011
Posts: 329

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
16 Sep 2011, 08:42
newmoon wrote: Please elaborate the solving method.
In a shop, 40% socks are white & rest are black. 60% socks are made of cotton & rest are made of wool. 25% white socks are made of cotton & 20 of the black socks are made of wool. how many are black socks are made of cotton? A)100 B)80 C)60 D)50 E)25 I'll prefer to solve this with plug n play method. As we know, White Cotton socks are only 25% and Total Cotton socks is 60%  Hence Black Cotton socks has to be [highlight]HIGH[/highlight]number. Thats why we've to pick high number... say 100 or 80. 100 fits perfectly after relevant calculations. Hence answer A. Cheers.
_________________
 What you do TODAY is important because you're exchanging a day of your life for it! 



Senior Manager
Joined: 03 Mar 2010
Posts: 377

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
16 Sep 2011, 12:47
Good solution viks4gmat. +1.
_________________
My dad once said to me: Son, nothing succeeds like success.



Director
Joined: 01 Feb 2011
Posts: 659

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
16 Sep 2011, 19:32
total cotton 60T/100
total wool 40T/100
black wool = 20
total white = 40T/100 total black = 60T/100
total = T
given 25% of white is cotton . => (25/100)(40T/100) = 10T/100
=> white and wool = (40T/100)  (10T/100) = 30T/100
=> black and cotton = 50T/100 = T/2
also given black and wool = 20 = > 10T/100 = 20 => T = 200
=> black and cotton = 200/2 = 100
Answer is A.



Intern
Joined: 17 Sep 2011
Posts: 4

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
20 Sep 2011, 05:18
Hi
I like this post:
You create good material for community.
Please keep posting



Manager
Status: mba here i come!
Joined: 07 Aug 2011
Posts: 207

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
03 Oct 2011, 12:26
let total socks = 100x w (white) = 40x, so b (black) = 60x c (cotton) = 60x, so wl (wool) = 40x wc (white + cotton) = 40x/4 = 10x so, wwl (white + wool) = 40x10x = 30x bwl (black + wool) = 40x30x = 10x > this is equal to 20 10x = 20 ...... x=2 bc (black + cotton) = 60x10x = 50x OR 50*2 = 100
_________________
press +1 Kudos to appreciate posts Download Valuable Collection of Percentage Questions (PS/DS)



Current Student
Joined: 08 Jan 2009
Posts: 304

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
03 Oct 2011, 18:21
All of the above approaches are great, but I always find these problems so much easier after making a table outlining all the information received. If you are not familiar with this method it is worth exploring. Step 1) Put all information as given into table. We represents unknowns as 'x'. It's important to note that from the information given, we are told that there are 20 Black & Woolen socks Step 2) Find an equation such that we can solve for x, solve for x Step 3) Put information back into table and pluck out the number we need, in this case 100.



Intern
Joined: 10 May 2011
Posts: 20
Location: India
Concentration: Strategy, General Management

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
03 Oct 2011, 20:51
newmoon wrote: Please elaborate the solving method.
In a shop, 40% socks are white & rest are black. 60% socks are made of cotton & rest are made of wool. 25% white socks are made of cotton & 20 of the black socks are made of wool. how many are black socks are made of cotton? A)100 B)80 C)60 D)50 E)25 Ok, let's try a different approach. We know that 60% of total socks(T) = Black socks (B). or we can rewrite it as 0.6 * T = B or T = B/0.6 or T = 10B/6 = 5B/3. Now, we know Total socks (T) can't be a fraction so B has to be a multiple of 3. Now we know B = Wool + Cotton or B = 20 + Cotton. Plug in the value of Cotton socks from options for which B becomes multiple of 3. Only options (A) & (E) are satisfying this criteria. For (E), T = 75 and white socks = 30. Now we know, 60% of the total socks are made from cotton i.e 60% of 75 = 45. Black cotton socks are 25 so white cotton socks should be 20 or 25% of 30 should be 20 which is not possible. So we can eliminate (E). Only option left is (A) I hope it helps!! Cheers!!



Intern
Joined: 04 Oct 2011
Posts: 9

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
05 Oct 2011, 09:17
In a shop, 40% socks are white & rest are black. 60% socks are made of cotton & rest are made of wool. 25% white socks are made of cotton & 20 of the black socks are made of wool. how many are black socks are made of cotton? A)100 B)80 C)60 D)50 E)25
White = 40 % Blank = 60 %
Cotton = 60% Wool = 40%
25 % of the total white socks are made of cotton,so 10 % of the total socks are white and cotton
Remaining 75 % of the White socks are wool.(30 % of overall)
10% of the wool socks are lack = 20
from here remaining 50% black socks are cotton = 5*20 = 100

Kudos if you feel it is good



Senior Manager
Joined: 08 Jun 2015
Posts: 436
Location: India
GMAT 1: 640 Q48 V29 GMAT 2: 700 Q48 V38
GPA: 3.33

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
13 May 2016, 08:05
Option A it is ... need a 2 by 2 matrix method ...
_________________
" The few , the fearless "



Board of Directors
Joined: 17 Jul 2014
Posts: 2621
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
16 May 2016, 18:52
newmoon wrote: In a shop, 40% socks are white and rest are black. 60% socks are made of cotton and rest are made of wool. 25% white socks are made of cotton and 20 of the black socks are made of wool. How many black socks are made of cotton?
A) 100 B) 80 C) 60 D) 50 E) 25 i used double matrix to solve it
Attachments
socks.jpg [ 15.53 KiB  Viewed 2398 times ]



NonHuman User
Joined: 09 Sep 2013
Posts: 9116

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
Show Tags
31 Aug 2018, 09:15
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: In a shop, 40% socks are white and rest are black. 60% socks are made &nbs
[#permalink]
31 Aug 2018, 09:15






