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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

In a shop, 40% socks are white and rest are black. 60% socks are made [#permalink]

Show Tags

16 Sep 2011, 08:10

1

This post received KUDOS

1

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

65% (hard)

Question Stats:

64% (03:06) correct
36% (02:39) wrong based on 92 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?

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! -----------------------------------------------------------------------------------------

Re: In a shop, 40% socks are white and rest are black. 60% socks are made [#permalink]

Show Tags

16 Sep 2011, 08:48

4

This post received KUDOS

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 = wh-ct => 0.3x = wh-wl

total wool is 0.4x => black wool socks = 0.4 x (total) - 0.3 x (wh-wl) = 0.1x given as 20

=> total number of socks = 200

= > total black socks = .6x = 120 total cotto black socks = 120 - 20 (bl-wl) = 100 hence A

Re: In a shop, 40% socks are white and rest are black. 60% socks are made [#permalink]

Show Tags

03 Oct 2011, 18:21

1

This post received KUDOS

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.

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)

Re: In a shop, 40% socks are white and rest are black. 60% socks are made [#permalink]

Show Tags

05 Oct 2011, 09:17

2

This post received KUDOS

1

This post was BOOKMARKED

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

Re: In a shop, 40% socks are white and rest are black. 60% socks are made [#permalink]

Show Tags

13 Feb 2015, 05:22

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.
_________________

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 637 times ]

gmatclubot

Re: In a shop, 40% socks are white and rest are black. 60% socks are made
[#permalink]
16 May 2016, 18:52

Happy New Year everyone! Before I get started on this post, and well, restarted on this blog in general, I wanted to mention something. For the past several months...

It’s quickly approaching two years since I last wrote anything on this blog. A lot has happened since then. When I last posted, I had just gotten back from...

Happy 2017! Here is another update, 7 months later. With this pace I might add only one more post before the end of the GSB! However, I promised that...

The words of John O’Donohue ring in my head every time I reflect on the transformative, euphoric, life-changing, demanding, emotional, and great year that 2016 was! The fourth to...