11 copies on Friday?

[sanju09]

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 the 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.



A GMATPrep question

[GMATGuruNY]

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 the 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.

A GMATPrep question

When a problem gives an upper or lower limit -- in this case, Friday = 11 -- plug in the limit in order to see how the problem is restricted.

Statement 1: Thursday = 8.
If Friday = 11:
Minimum value for Sun-Weds = 1+2+3+4 = 10, making Saturday 90-8-11-10 = 61.
If Friday = 12:
Minimum value for Sun-Weds = 1+2+3+4 = 10, making Saturday 90-8-12-10 = 60.
Insufficient.

Statement 2: Saturday = 38.
If Friday = 11:
Sun-Thurs = 90-38-11 = 41.
Maximum value for Sun-Thurs = 10+9+8+7+6 = 40.
Thus, more books must be sold on Friday, so Friday > 11.
Sufficient.

The correct answer is B.