Store S sold a total of 90 copies of a certain book during the seven days last week and it sold different numbers...

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BTGmoderatorLU: Moderator; Posts: 2505; Joined: Sun Oct 15, 2017 1:50 pm; Followed by:6 members

Store S sold a total of 90 copies of a certain book during the seven days last week and it sold different numbers...

by BTGmoderatorLU » Wed Aug 05, 2020 4:08 am

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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 Friday, did Store S sell more than 11 copies on Friday?

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

The OA is B

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Source: Beat The GMAT — Data Sufficiency | Wed Aug 05, 2020 4:08 am

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Jay@ManhattanReview: GMAT Instructor; Posts: 3008; Joined: Mon Aug 22, 2016 6:19 am; Location: Grand Central / New York; Thanked: 470 times; Followed by:34 members

Re: Store S sold a total of 90 copies of a certain book during the seven days last week and it sold different numbers...

by Jay@ManhattanReview » Thu Aug 06, 2020 1:13 am

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BTGmoderatorLU wrote: ↑
Wed Aug 05, 2020 4:08 am
Source: GMAT Prep

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 Friday, did Store S sell more than 11 copies on Friday?

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

The OA is B

So, we are given that

S'+M+T+W+Th+F+S = 90, where S', M, T... are no. of copies sold on days of the week.

We are given that S = greatest and F < S.

We have to ascertain whether F > 11.

Let's take each statement one by one.

1) Last week Stores S sold 8 copies on Thursday.

From S'+M+T+W+Th+F+S = 90, we have S'+M+T+W+F+S = 82

Case 1: F not greater than 11.

1+2+3+4+11+61 = 82 --- possible. The answer is No.

Case 2: F > 11.

1+2+3+4+12+60 = 82 --- possible. The answer is Yes.

No unique answer. Insufficient.

2) Last week Store S sold 38 copies on Saturday.

From S'+M+T+W+Th+F+S = 90, we have S'+M+T+W+Th+F = 52

Case 1: F not greater than 11.

6+7+8+9+10+11 = 51 ≠ 52 --- not a possible case

Since taking F = 11, we took maximum possible values for M, T, W, and Th, yet the total is less, we must have F = 12 > 11. The answer is yes. SUfficient.

Correct answer: B

Hope this helps!

-Jay
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