Wordy Data Sufficiency

BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

This topic has expert replies

Post new topic Post Reply

Previous Topic Next Topic

Apl28: Newbie | Next Rank: 10 Posts; Posts: 5; Joined: Sat Jun 28, 2008 10:38 am

Wordy Data Sufficiency

by Apl28 » Tue Dec 02, 2008 8:22 pm

Store S sold a total of 90 copies of a certain book during the seven days last week and it sold different numbers of copies on any 2 days. If for the seven days Store S sold the greatest number of copies on Saturday and the second greatest number of copies on Firday, did Store S sell more than 11 copies on Friday?

1) Last week Store S sold 8 copies on Thursday
2) Last week Store S sold 38 copies on Saturday

[spoiler]B
[/spoiler]

Quote

Source: Beat The GMAT — Data Sufficiency | Tue Dec 02, 2008 8:22 pm

anayeri: Senior | Next Rank: 100 Posts; Posts: 47; Joined: Wed Oct 08, 2008 11:29 am; Location: Toronto, Ontario; Thanked: 5 times

by anayeri » Tue Dec 02, 2008 8:49 pm

Statement 1)

We want to use this statement to see if on the minimum, Friday sold 12+ copies. Let's assume Thursday was the third highest day, could Friday have sold less than 12 copies? Let's see:

Su Mo Tu We Th Fr(++)
4 5 6 7 8 11, so this would make Saturday 49 to get to 90, so yes, Friday COULD have sold let's than 12 copies. So insufficient.

Statement 2)

We know that the higest day (Saturday) sold 38 copies. Given that, can we prove that the second highest day (friday) had less than 12 copies sold, while maximizing the other days? Let's see:

Su Mo Tu We Th Fr(++) Sa(+)
6 7 8 9 10 11 38

The sum of these numbers (89) falls 1 short of 90 - so, Friday must have sold atleast 12 copies.

Answer B.
[/quote]

Quote

missrochelle: Master | Next Rank: 500 Posts; Posts: 117; Joined: Wed Jun 09, 2010 7:02 am

by missrochelle » Sat Aug 28, 2010 3:42 pm

in this question...how are we "proving" that more than 11 copies were sold by setting friday equal to 11 and testing whether they sold "less than 12". i dont understand the wording....

Quote

kevincanspain: GMAT Instructor; Posts: 613; Joined: Thu Mar 22, 2007 6:17 am; Location: madrid; Thanked: 171 times; Followed by:64 members; GMAT Score:790

by kevincanspain » Mon Aug 30, 2010 12:20 am

missrochelle wrote:in this question...how are we "proving" that more than 11 copies were sold by setting friday equal to 11 and testing whether they sold "less than 12". i dont understand the wording....

Good question!

It is apparent from (2) that more than 11 copies could have been sold on Friday (it may be that few copies were sold during the rest of the week). The question is "Must it be true that more than 11 were sold on Friday?"

We can answer this question by seeing whether it is possible that exactly 11 were sold on Friday. We find out that if exactly 11 were sold on Friday, at most 89 were sold during the week, not 90 as stated in the text.

Thus the possibility that the answer to the question is no is inconsistent with the facts given, meaning that the answer must be yes.

Kevin Armstrong
GMAT Instructor
Gmatclasses
Madrid

Quote

gmatmachoman: Legendary Member; Posts: 2326; Joined: Mon Jul 28, 2008 3:54 am; Thanked: 173 times; Followed by:2 members; GMAT Score:710