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GMAT Prep Q - Books

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GMAT Prep Q - Books

by tito1545 » Tue Mar 08, 2011 2:29 pm
A step by step solution for this please :

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 no 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


ans B
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Source: — Data Sufficiency |
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by Tani » Tue Mar 08, 2011 3:20 pm
Are you sure this question was copied properly.

Look at statement 2. If Friday sold the most, and Saturday sold 38, Friday had to sell at least 39. That would make the second statment sufficient.
However, That leaves only 13 books for the other five days. Since they all sold different numbers, using 1,2,3, and 4 for Monday, Tuesday, Wednesday, and Thursday, leaves only three books. Since you can't sell the same number any two days, Sunday would have to sell 0 and the remaining three be sold on the first four days being sure not to sell the same number twice. (e.g.1,3,4,5, or 1,2,3,7.)

Statement 1, however, should also work. If Thursday sold 8, there were 82 sold the remaining 6 days. They would have to average just under 16 books per day, and if Friday sold the most it would have to sell more than 16 - therefore more than 11. So statement q should work also.
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by tito1545 » Tue Mar 08, 2011 3:43 pm
Apologies Tani , I did miss something :

I have now corrected the 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 no 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 Tani » Tue Mar 08, 2011 4:04 pm
Okay - so statement 2 tells us we have 38 on Saturday - that leave 52 - an average slightly below 9 per day for the other 6 days.
try 6+7+8+9+10+11 = 51 still need one more - the second highest (Friday) must have at least 12. (If you add the last one to any of the other days you will have two days with the same number of books sold.


Looking at statement 1 - If Thursday sells 8, Friday could sell 9, then M/T/W/Sun = could sell 4, 5, 6, and 7 leaving 51 for Saturday.
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