Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 05 Jul 2015, 13:40

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Bill Gates bough several pencils. If each pencil was either

Author Message
TAGS:
Intern
Joined: 22 Sep 2007
Posts: 28
Followers: 0

Kudos [?]: 4 [0], given: 0

Bill Gates bough several pencils. If each pencil was either [#permalink]  28 Feb 2008, 16:32
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
Bill Gates bough several pencils. If each pencil was either a 23 cent pencil or a 21 cent pencil, how many 23 cent pencil did Bill Gates Buy

1 – Bill Gates bought a total of 6 pencils.
2 – The total value of pencils Bill Gates bought was 130 cents
Intern
Joined: 09 Feb 2008
Posts: 14
Followers: 0

Kudos [?]: 0 [0], given: 1

Re: DS - Bill Gates [#permalink]  28 Feb 2008, 17:08
E). Not enough data i suppose..

but i suppose we could do it by trying out different combinations of pencils that add up to 6 pencils, and see which one gives exactly 130, and get the answer.. but that is not mathematically defined right?
Intern
Joined: 25 Feb 2008
Posts: 14
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: DS - Bill Gates [#permalink]  28 Feb 2008, 17:15
23*x+21*(6-x) = 130
2x +126 = 130
x= 2

Director
Joined: 23 Sep 2007
Posts: 793
Followers: 5

Kudos [?]: 108 [0], given: 0

Re: DS - Bill Gates [#permalink]  28 Feb 2008, 17:16
it is B

a total of 130 cents

meaning that there are 6 pencils together, 2 23cents pencils and 4 21cents pencils.

This is a gmatprep question, someone substituted the name "bill gates" in place of "marta"

Last edited by gmatnub on 28 Feb 2008, 19:11, edited 1 time in total.
Manager
Joined: 05 Feb 2007
Posts: 140
Followers: 1

Kudos [?]: 7 [0], given: 7

Re: DS - Bill Gates [#permalink]  28 Feb 2008, 17:58
gmatnub wrote:
it is B

a total of 130 cents

meaning that there are 6 pencils together, 2 23cents pencils and 4 21cents pencils.

This is a gmatprep question, someone substituted the name "bill gates" in place of "maria"

What was your logic going from 130, to knowing there were 6 pencils.
VP
Joined: 22 Oct 2006
Posts: 1443
Schools: Chicago Booth '11
Followers: 8

Kudos [?]: 156 [0], given: 12

Re: DS - Bill Gates [#permalink]  29 Feb 2008, 08:12
B

21 cent pencils

21 - 1 pencil
42 - 2 pencil
63- 3 pencil
84- 4 pencil
105- 5 pencil

23 cent pencils

23- 1 pencil
46- 2 pencil
69- 3 pencil
92- 4 pencil
115- 5 pencil

The only combination of these pencils that add up to 130 is

4 21 cent pencils and 2 23 cent pencils = 84+46cents = 130 cents

quickly look at the last digits to see what adds up and gives you a value of 0 between them instead of adding each combination up.
Director
Joined: 10 Sep 2007
Posts: 948
Followers: 7

Kudos [?]: 213 [0], given: 0

Re: DS - Bill Gates [#permalink]  29 Feb 2008, 08:19
Statement 1:

Tells us total 6 pencils are purchased but does not provide how many of these are 21 cent pencils and how many are 23 cents pencil.

Statement 2:

Tells us total of 130 cents are spent but in what proportion is not mentioned.

Now combine Both Statement 1 & 2

Assume total 21 cent pencils are X, so total 23 cents pencils will be (6-X), as total pencils are 6 (from statement 1).

Now Total cost = 21*X + 23*(6-X) = 130 => X = 4

So total 23 cents pencils are 2.

Manager
Joined: 27 Jun 2007
Posts: 200
Followers: 3

Kudos [?]: 19 [0], given: 0

Re: DS - Bill Gates [#permalink]  29 Feb 2008, 08:26
abhijit_sen wrote:
Statement 1:

Tells us total 6 pencils are purchased but does not provide how many of these are 21 cent pencils and how many are 23 cents pencil.

Statement 2:

Tells us total of 130 cents are spent but in what proportion is not mentioned.

Now combine Both Statement 1 & 2

Assume total 21 cent pencils are X, so total 23 cents pencils will be (6-X), as total pencils are 6 (from statement 1).

Now Total cost = 21*X + 23*(6-X) = 130 => X = 4

So total 23 cents pencils are 2.

I agree with this response and calculation.
Director
Joined: 26 Jul 2007
Posts: 541
Schools: Stern, McCombs, Marshall, Wharton
Followers: 5

Kudos [?]: 121 [0], given: 0

Re: DS - Bill Gates [#permalink]  29 Feb 2008, 11:36
RyanDe680 wrote:
abhijit_sen wrote:
Statement 1:

Tells us total 6 pencils are purchased but does not provide how many of these are 21 cent pencils and how many are 23 cents pencil.

Statement 2:

Tells us total of 130 cents are spent but in what proportion is not mentioned.

Now combine Both Statement 1 & 2

Assume total 21 cent pencils are X, so total 23 cents pencils will be (6-X), as total pencils are 6 (from statement 1).

Now Total cost = 21*X + 23*(6-X) = 130 => X = 4

So total 23 cents pencils are 2.

I agree with this response and calculation.

I'm confused when answering these problems as well.

When reading this problem if we assume that X is the number of 21 cent pencils and Y is the number of 23 cent pencils then we get this from the the statements.

1. X+Y=6
2. 21X+23Y=130

This is a common problem on the gmat and 99% of the time you clearly need two equations to solve becasue there are two variables. So a quick glance will give you the answer C. The problem is that in some cases (this being one of them) there is only one possible combination and it can therefore be deduced from stmt 2 alone. I cant figure out a quick systematic way of determening which is which. Becasue most of the prep courses tell you to stop DS problems as soon as you figure out you have enough information without solving.
Manager
Joined: 05 Feb 2007
Posts: 140
Followers: 1

Kudos [?]: 7 [0], given: 7

Re: DS - Bill Gates [#permalink]  12 Mar 2008, 22:20
anyone help with a solid approach to these?
Manager
Joined: 19 Dec 2007
Posts: 87
Followers: 1

Kudos [?]: 22 [0], given: 0

Re: DS - Bill Gates [#permalink]  13 Mar 2008, 01:11
terp26 wrote:
B

21 cent pencils

21 - 1 pencil
42 - 2 pencil
63- 3 pencil
84- 4 pencil
105- 5 pencil

23 cent pencils

23- 1 pencil
46- 2 pencil
69- 3 pencil
92- 4 pencil
115- 5 pencil

The only combination of these pencils that add up to 130 is

4 21 cent pencils and 2 23 cent pencils = 84+46cents = 130 cents

quickly look at the last digits to see what adds up and gives you a value of 0 between them instead of adding each combination up.

This one is a good explanation. I agree..
Director
Joined: 10 Sep 2007
Posts: 948
Followers: 7

Kudos [?]: 213 [0], given: 0

Re: DS - Bill Gates [#permalink]  13 Mar 2008, 06:09
Gixxer you are making a assumption that 2nd alone is giving you both the equations, however truth is 2nd statement alone is giving you only 21X+23Y=130.

It is from 1st statement that you are getting X+Y=6, which you canno include as part of statement 2, when considering it on it own.

As you require both the equations, to get the answer, so answer is C.
Manager
Joined: 31 Oct 2007
Posts: 113
Location: Frankfurt, Germany
Followers: 1

Kudos [?]: 30 [1] , given: 0

Re: DS - Bill Gates [#permalink]  13 Mar 2008, 08:00
1
KUDOS
kizito2001 wrote:
Bill Gates bough several pencils. If each pencil was either a 23 cent pencil or a 21 cent pencil, how many 23 cent pencil did Bill Gates Buy

1 – Bill Gates bought a total of 6 pencils.
2 – The total value of pencils Bill Gates bought was 130 cents

GiantSwan,
To tackle such question, start with the question stem. You know there are 3 variables you need to know and the variable that you are looking for is no. of 23 cent pencils?

Let x be the no. of 23 cent pencil
Let y be the no. of 21 cent pencil

23x + 21y = ?

Statement 1: x + y = 6 -----> this gives you a clue that Bill bought 6 pencils but not sure the combination. Thus, this statement alone can't answer the question.

Statement 2: Total value of pencil = 130 cents ie 23x + 21y = 130. Still, this statement alone does not answer the question.

If we combine the hints from statement 1 and 2, we can solve

y = (6 - x)
=> 23x + 21(6 - x) = 130
=> 23x + 126 - 21x = 130
=> 2x = 130 - 126
=> 2x = 4
Thus, x = 2

Ans: C - both statements together are sufficient but neither statement alone is sufficient.

The trick is convert all statements into algrebric (?) statement.
_________________

Jimmy Low, Frankfurt, Germany
Blog: http://mytrainmaster.wordpress.com
GMAT Malaysia: http://gmatmalaysia.blogspot.com

Manager
Joined: 31 Oct 2007
Posts: 113
Location: Frankfurt, Germany
Followers: 1

Kudos [?]: 30 [0], given: 0

Re: DS - Bill Gates [#permalink]  17 Mar 2008, 18:11
Anyone has other answers? I rechecked and sticking to "C". Perhaps the answer sheet is wrong.
_________________

Jimmy Low, Frankfurt, Germany
Blog: http://mytrainmaster.wordpress.com
GMAT Malaysia: http://gmatmalaysia.blogspot.com

SVP
Joined: 29 Aug 2007
Posts: 2493
Followers: 59

Kudos [?]: 577 [0], given: 19

Re: DS - Bill Gates [#permalink]  17 Mar 2008, 20:44
kizito2001 wrote:
Bill Gates bough several pencils. If each pencil was either a 23 cent pencil or a 21 cent pencil, how many 23 cent pencil did Bill Gates Buy

1 – Bill Gates bought a total of 6 pencils.
2 – The total value of pencils Bill Gates bought was 130 cents

B too.

xa + yb = 130
23a + 21b = 130

plug-in:
23x2 + 21x4 = 130
46 + 84 = 130

bingo: a = 2 and b = 4. so altogather 6 pencils.
_________________
Re: DS - Bill Gates   [#permalink] 17 Mar 2008, 20:44
Similar topics Replies Last post
Similar
Topics:
25 Martha bought several pencils. If each pencil was either a 18 01 Sep 2010, 09:02
Marta bought several pencils. If each pencil was either a 4 16 Nov 2009, 20:52
Martha bought several pencils. If each pencil was either a 1 15 Mar 2008, 04:45
Marta bought several pencils. If each pencil was either 2 02 Oct 2007, 12:22
Marta bought several pencils. If each pencil was either a 8 13 Jun 2007, 07:36
Display posts from previous: Sort by