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DS question

by Beat-D-GMAT » Sun Jan 03, 2010 9:18 am
Hello. Can some one please explain how to solve this question.

Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did Store S sell more than 11 copies on Friday?

(1) Last week Store S sold 8 copies of the book on Thursday.
(2) Last week Store S sold 38 copies of the book on Saturday.
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by gmattic » Sun Jan 03, 2010 9:34 pm
Is the answer C?

(1) in-sufficient on its own
(2) in-sufficient on its own

(1) & (2) :
90 - 38 - 8 = 44 copies can be sold over the 5 remaining days (including Friday)

44 copies over 5 remaining days : 44/5 = 8.8 copies must be sold per day for the remaining 5 days. but you know that that F is second largest day. so copies sold on Friday have to be greater than copies sold on any other day but Saturday.

assume that 8 copies are sold on M-T & Sunday, that's 8 * 5 = 40, which means there are 90-40-38 copies remaining that can be sold on Friday, they are: 12

however it doesn't have to be that way, can you prove that you can have 11 copies sold on Friday, 38 on Sat, 8 on Thurs while still letting Friday be the second highest?

90-38-11-8 = 57 copies that can be sold on the remaining 4 days.
57/4 = 14.something > 11

the average copies sold across those four days is 14, which means one of the days has be more than 11, which voilates the rule.

Therefore, with (1) & (2), if the second greatest number of copies are sold on Friday, then more than 11 copies had to be sold on Friday. Hence, the answer is C.
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by gmatmachoman » Mon Jan 04, 2010 12:33 am
Good Reply .

C would the right option!!

Sunday, Mon,Tue,Wed can take any values less than 11 as Friday only can be the second highest as mentioned in the question stem.

And to sum up to 90 copies we need to have Friday to be greater than 11.
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by vinamra » Mon Jan 04, 2010 5:07 am
I don't think so!

My answer is Option B

Explanation :

Statement 1 results in various Sales Value on Friday!

So option B C E remains

Statement 2:

90-Saturday (38)= 52

No Days are equal, so lets plug-in Maximum values for Sun, Mon, Tue, Wen,Thur so that we can get minimum possible of Friday...
also remember,
1) No two sales figure are same!
2) Friday has second highest Sales while, Saturday has Highest sale

Maximum values

Sunday= 10
Monday=9
Tuesday=8
Wednesday=7
Thursday= 6

Sum= 40

So, 90-38-40=Friday
Friday = 12

Now you can jumble up Values of Other days such that they doesnt exceed value of Friday!

So, the Answer is Option B

if some experienced instructor can put some light on this question, is most appreciated!
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by Testtrainer » Mon Jan 04, 2010 7:07 pm
Beat-D-GMAT wrote:Hello. Can some one please explain how to solve this question.

Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did Store S sell more than 11 copies on Friday?

(1) Last week Store S sold 8 copies of the book on Thursday.
(2) Last week Store S sold 38 copies of the book on Saturday.
The answer should be C. I think the best way would be to pick numbers.

Statement 1) Thursday = 8
If Friday = 12, then Saturday could be 60 and the remaining days could be 1, 2, 3, and 4
If Friday = 11, then Saturday could be 61 and the remaining days could be 1, 2, 3, and 4
Insufficient because we have a "yes" (Friday = 12) and a "no" (Friday = 11)

Statement 2) Saturday = 38
If Friday = 12, then the remaining days could be 2, 3, 5, 9, 10, and 11
If Friday = 11, then the remaining days could be 2, 4, 5, 9, 10, and 11
Insufficient because we have a "yes" and a "no".

Statements combined: Thursday = 8, Saturday = 38
If Friday = 12, then the remaining days could be 1, 2, 8, 10, and 11
If Friday = 11, then the remaining days could NOT be properly assigned.
The largest any remaining day = 10 (because Friday is second largest) and no remaining day = 8
(because Thursday = 8), the remaining days at most could be 10, 9, 7, and 6. BUT 10 + 9 + 7 + 6 = 32.
AND 32 + 8 + 38 + 11 = 89. We need to get to a total of 90, which is impossible here.
Anything lower than 11 will cause the same problems.
Sufficient because always "yes" (Friday > 11).
Answer = (C)

Hope this helps.
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by vinamra » Mon Jan 04, 2010 9:01 pm
Testtrainer wrote:
Beat-D-GMAT wrote:Hello. Can some one please explain how to solve this question.

Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did Store S sell more than 11 copies on Friday?

(1) Last week Store S sold 8 copies of the book on Thursday.
(2) Last week Store S sold 38 copies of the book on Saturday.
Statement 2) Saturday = 38
If Friday = 12, then the remaining days could be 2, 3, 5, 9, 10, and 11
If Friday = 11, then the remaining days could be 2, 4, 5, 9, 10, and 11
Insufficient because we have a "yes" and a "no".



Dude, if Friday = 12, then the remaining days could be Sunday= 2 Monday = 3, Tuesday = 5 Wednesday = 9 Thursday = 10, Saturday = 38

So the TOTAL is 79....so where is other 11 books sold?

Pls check your post, you have taken "Additional Day"
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by kevincanspain » Wed Jan 06, 2010 10:41 am
Beat-D-GMAT wrote:Hello. Can some one please explain how to solve this question.

Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did Store S sell more than 11 copies on Friday?

(1) Last week Store S sold 8 copies of the book on Thursday.
(2) Last week Store S sold 38 copies of the book on Saturday.
Call x1, x2, ..., x7 the numbers of books sold on the seven days of the week in ascending order.

Note that x1 < x2 < x3 < ... < x7

x7 corresponds to Saturday and x6 to Friday

Given x1 + x2 + ... + x7 = 90 is x6 > 11 ?

(1) tells us that x6 > 8 NOT SUFF
(2) x7 = 38, thus x1 + x2 + ... + x6 = 52 (a)
Certainly x6 could be greater than 11, but could it be exactly 11 ?
In that case, the largest possible sum for x1 + x2 + ... x5 would be 6 + 7+ 8+ 9+ 10 = 40
Thus x1 + x2 + ... + x6 would be less than 52, which contradicts (a)
Nor can x6 be less than 11, for the same reasoning.
So we see that x6 must be greater than 11 SUFF
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by arora007 » Sat Jul 31, 2010 5:44 am
Yes.. B is the answer... a wonderful problem from GMATFix.
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by reply2spg » Thu Aug 05, 2010 11:36 am
B must be the answer
Beat-D-GMAT wrote:Hello. Can some one please explain how to solve this question.

Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did Store S sell more than 11 copies on Friday?

(1) Last week Store S sold 8 copies of the book on Thursday.
(2) Last week Store S sold 38 copies of the book on Saturday.
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