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# In a two-month survey of shoppers, each shopper bought one of two bran

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Intern
Joined: 09 Apr 2018
Posts: 27
Location: India
Concentration: Strategy, Finance
In a two-month survey of shoppers, each shopper bought one of two bran  [#permalink]

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09 Apr 2019, 04:24
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100% (01:52) correct 0% (00:00) wrong based on 2 sessions

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In a two-month survey of shoppers, each shopper bought one of two brands of detergent, X or Y, in the first month and again bought one of these brands in the second month. In the survey, 90 percent of the shoppers who bought Brand X in the first month bought Brand X again in the second month, while 60 percent of the shoppers who bought Brand Y in the first month bought Brand Y again in the second month. What percent of the shoppers bought Brand Y in the second month?

1.In the first month, 50 percent of the shoppers bought Brand X.
2.The total number of shoppers surveyed was 5,000.
Intern
Joined: 17 Sep 2018
Posts: 38
Re: In a two-month survey of shoppers, each shopper bought one of two bran  [#permalink]

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09 Apr 2019, 04:40
I am "quant-cautioned" so the thinking might help some, but not others (and no guarantees that it is correct -it may be wrong):

1. Instinctively I thought it might be useful to draw a two-variable matrix. I was wrong - (would it be X, not X, Y, not Y - how would we account for the second month etc.);

2. So I used a decision tree diagram (which I find useful in day-to-day thinking) sketching out a line for X for Month 1 and a line for Y for the same month. Then each line would split for two more lines to account for people either buying or not buying X or Y, having purchased it in the previous month. Within any DS, the wording is important: we are told here that "each shopper bought one of two brands of detergent, X or Y," That means that if a certain bought X, then they did not buy Y (emphasis on the 'either....or' in the Question). Therefore linking it back to S1, we can see that if they chose 50% of X, then 50% picked Y. For S2, one should be careful when seeing values in the statements but not the question - worth looking at the question again to see if we need a percentage or a value.
Intern
Joined: 04 Aug 2016
Posts: 8
In a two-month survey of shoppers, each shopper bought one of two bran  [#permalink]

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09 Apr 2019, 05:20
The question mentions that the shoppers bought either brand X or Y during month 1 as well as on month 2.
Now it's asking for the percentage that bought brand Y during the month 2.

Statement 1
First month brand X = 50%, so Brand Y= 50%,
Now for second month, brand Y was retained by 60%. So that would be 30% of the total shoppers.
Also 10% of the brand X buyers switched to brand Y. So that is 10% of 50% i.e 5%.
So the total is 30% + 5% = 35%
So statement 1 is sufficient.

Statement 2.
Just gives the information of the total shoppers i.e 5000
No other information is given.
So not possible with statement 2.

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Joined: 02 Sep 2009
Posts: 55277
Re: In a two-month survey of shoppers, each shopper bought one of two bran  [#permalink]

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09 Apr 2019, 08:13
lynnglenda wrote:
In a two-month survey of shoppers, each shopper bought one of two brands of detergent, X or Y, in the first month and again bought one of these brands in the second month. In the survey, 90 percent of the shoppers who bought Brand X in the first month bought Brand X again in the second month, while 60 percent of the shoppers who bought Brand Y in the first month bought Brand Y again in the second month. What percent of the shoppers bought Brand Y in the second month?

1.In the first month, 50 percent of the shoppers bought Brand X.
2.The total number of shoppers surveyed was 5,000.

Discussed here: https://gmatclub.com/forum/in-a-two-mon ... fl=similar
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Re: In a two-month survey of shoppers, each shopper bought one of two bran   [#permalink] 09 Apr 2019, 08:13
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