GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Jun 2019, 22:01 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  200 people responded to a survey that asked them to rank three differe

Author Message
TAGS:

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 55618
200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

25 00:00

Difficulty:   95% (hard)

Question Stats: 36% (03:01) correct 64% (03:02) wrong based on 88 sessions

HideShow timer Statistics 200 people responded to a survey that asked them to rank three different brands of soap. The percentage of respondents that ranked each brand 1st, 2nd, and 3rd are listed above. If no respondents rated the soaps in the order Y, Z, X, how many respondents rated the soap in the following order: X, Y, Z?

A. 100
B. 60
C. 50
D. 30
E. 25

Kudos for a correct solution.

Attachment: Brand_Rankings.png [ 34.63 KiB | Viewed 5293 times ]

_________________
e-GMAT Representative D
Joined: 04 Jan 2015
Posts: 2888
Re: 200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

7
5
The question looks a bit data heavy, but one strike at the right place immediately gives you the answer.

Given
We are given a set of data with user's preferences of three brands of soaps X, Y & Z. We are told that 200 people responded to the survey with none of them having preference in the order Y,Z,X. We are asked to find the number of respondents who rated the soap in the order of X,Y,Z.

Approach
We are given total number of responses of people at each rank. The key to note here is that people can only vote for soaps in a rank for which they have not voted earlier. For example, if a person has voted soap X as rank 1, he can't vote for soap X again in any of the subsequent ranks. As an extension to this, we can say that people who voted for soap x as rank 2 would have voted for either soap Y or soap Z as rank 1.

We will use this concept along with the fact that no one ranked the soaps in the order of Y, Z, X to find out the number of people who ranked the soaps in the order of X, Y, Z.

Working Out
We are given that no one ranked the soaps in the order Y,Z,X. We also know that 60 i.e. 30% of 200 people ranked soap Y as 1. People who ranked soap Y as 1 did not rank soap Z as 2 which implies that all of them ranked soap X as 2. These people then further ranked soap Z as 3. Note here that these people can't vote for soap X or soap Y as rank 3 because they have earlier ranked soap X & soap Y.

We also know the total number of people who ranked soap Z as 3 is 55% of 200 i.e. 110. Soap Z can be ranked 3 by people who voted for soap X or soap Y as rank 1. Out of these we know that 60 people who voted for soap Y as rank 1, voted for soap Z as rank 3. This leaves 110 - 60 = 50 people who voted for soap Z as rank 3. This can only come from people who voted for soap X as rank 1 and then soap Y as rank 2.

Thus, we know that there were 50 people who ranked in the soaps in the order X, Y, Z  The other blocks in the tree structure do not need to be calculated (although they hardly take any time). They have been calculated here just for your reference.

Hope its clear!

Regards
Harsh
_________________
General Discussion
Math Expert V
Joined: 02 Sep 2009
Posts: 55618
Re: 200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

2
1
Bunuel wrote: 200 people responded to a survey that asked them to rank three different brands of soap. The percentage of respondents that ranked each brand 1st, 2nd, and 3rd are listed above. If no respondents rated the soaps in the order Y, Z, X, how many respondents rated the soap in the following order: X, Y, Z?

A. 100
B. 60
C. 50
D. 30
E. 25

Kudos for a correct solution.

Attachment:
Brand_Rankings.png

VERITAS PREP OFFICIAL SOLUTION:

In a way this problem is a permutations problem in disguise. When you're given the caveat that no one responded in the order Y, Z, X, you can tell a few things:

Anyone who put Y first did so in the order Y, X, Z (because there are only two ways to arrange X and Z if Y is in the first spot, and one of those was expressly prohibited by the prompt).

And, similarly, anytime that Z was second the order was X, Z, Y (because Y and Z couldn't have been arranged in the other order with Z fixed in the middle); and anytime X was last the order had to be Z, Y, X (because the other "X third" option is prohibited).

So if you follow that logic, your next step is to pick one of those certainties (for example, for all 60 cases of Y first - Y was first in 30% of the 200 cases - the order was Y, X, Z) and incorporate the statistics. That means that of the 110 cases of Z going last, 60 of them were in the order Y, X, Z. Which then means that, since the only other way to fix Z at the last spot is to go in the asked-about order X, Y, Z, the other 50 cases of Z third have to have come from the X, Y, Z order. Therefore, the answer is 50.
_________________
Intern  B
Joined: 20 Jun 2018
Posts: 46
Re: 200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

3
A very good question. Here is my approach:

Order of choices people can make -

X Y Z
X Z Y
Y X Z
Y Z X = 0 people made this choice
Z X Y
Z Y X

People who ranked X number 1 = 40% of 200 = 80. This implies that the sum of X Y Z & X Z Y is equal to 80.

People who ranked Y number 1 = 30% of 200 = 60. This implies that the sum of Y X Z & Y Z X is equal to 60. Since Y Z X is 0, this implies that the number of people who picked the order Y X Z is 60.

People who ranked Z number 3 = 55% of 200 = 110. This implies that the sum of Y X Z & X Y Z is equal to 110. Since Y X Z is 60, this implies that X Y Z =50. Therefore, the correct answer is C.
Attachments Solution.png [ 3.07 KiB | Viewed 1635 times ]

Manager  B
Joined: 12 Mar 2018
Posts: 124
Re: 200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

1
I felt dumb, I couldn t get how you infer "people who ranked Y number 1 = 30% of 200 = 60." from the graphs? maybe cause it's late here
Manager  G
Joined: 28 May 2018
Posts: 124
Location: India
Schools: Tuck '21, ISB '20, NTU '20
GMAT 1: 640 Q45 V35 GMAT 2: 670 Q45 V37 Re: 200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

1
faltan wrote:
I felt dumb, I couldn t get how you infer "people who ranked Y number 1 = 30% of 200 = 60." from the graphs? maybe cause it's late here

Question states:
200 people responded to a survey that asked them to rank three different brands of soap. The percentage of respondents that ranked each brand 1st, 2nd, and 3rd are listed above.
If no respondents rated the soaps in the order Y, Z, X, how many respondents rated the soap in the following order: X, Y, Z?

Given:
The first graph tells up how many people rated each brand of soap number 1:
40% rated X number 1. 30% rated Y number 1 and 30% rated Z number 1.

The second graph tells up how many people rated each brand of soap number 2:
45% rated X number 2. 40% rated Y number 2 and 15% rated Z number 2.

The third graph tells up how many people rated each brand of soap number 1:
15% rated X number 3. 30% rated Y number 3 and 55% rated Z number 3.

YZX = 0. ---- eq (1)

Calculations
15% = 30 people rated Z number 2. Possible combinations with Z in middle is XZY or YZX. So, 30 people voted for XZY because no respondents rated the soaps in the order Y, Z, X.
Basically,
XZY + YZX = 30 ,
From eq(1) we get XZY + 0 = 30 ,
XZY = 30 --- eq (2)

40% = 80 people rated X number 1. These people voted for XYZ or XZY .
Basically,
XYZ + XZY = 80.
From eq (2), we get XZY = 30 .
XYZ + 30 = 80.
So, XYZ = 50.
_________________
Please award KUDOS if my post helps. Thank you.
Intern  B
Joined: 20 Feb 2018
Posts: 16
Re: 200 people responded to a survey that asked them to rank three differe  [#permalink]

Show Tags

Mike03 wrote:
A very good question. Here is my approach:

Order of choices people can make -

X Y Z
X Z Y
Y X Z
Y Z X = 0 people made this choice
Z X Y
Z Y X

People who ranked X number 1 = 40% of 200 = 80. This implies that the sum of X Y Z & X Z Y is equal to 80.

People who ranked Y number 1 = 30% of 200 = 60. This implies that the sum of Y X Z & Y Z X is equal to 60. Since Y Z X is 0, this implies that the number of people who picked the order Y X Z is 60.

People who ranked Z number 3 = 55% of 200 = 110. This implies that the sum of Y X Z & X Y Z is equal to 110. Since Y X Z is 60, this implies that X Y Z =50. Therefore, the correct answer is C.

Hi Mike03, How is 'People who ranked Z number 3 = 55% of 200 = 110'? Re: 200 people responded to a survey that asked them to rank three differe   [#permalink] 13 Jun 2019, 08:08
Display posts from previous: Sort by

200 people responded to a survey that asked them to rank three differe  