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

Redeem

gmatprep 1 convention attendees

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 122
Joined: Mon Dec 15, 2008 12:03 am
Thanked: 2 times

gmatprep 1 convention attendees

by vkb16 » Tue Feb 17, 2009 4:26 am
the attendees at a certain convention purchased a total of 15,000 books. How many of these attendees were female?

1. there was a total of 4000 attendees at the convention
2. the male attendees purchased an average (a. mean) of 3 books each, and the female attendees purchased an average of 5 books each.

i think E

ans is C

please help me understand the reason
Top
Source: — Data Sufficiency |
User avatar
Site Admin
Posts: 2567
Joined: Thu Jan 01, 2009 10:05 am
Thanked: 712 times
Followed by:550 members
GMAT Score:770

by DanaJ » Tue Feb 17, 2009 4:39 am
Say we use the following notations:
t = total number of books
m = male buyers
f = female buyers
ma = average number of books bought by male buyers
fa = average number of books bought by female buyers
You get that t = m*ma + f*fa = 15 000 and you are looking for f.
1. tells us that m + f = 4 000. However, we do not have any additional info regarding the relationship between m and f. This is why 1 is insufficient.
2. means that ma = 3 and fa = 5, making t = 3m + 5f = 15 000. This doesn't help establish f either, since you don't know any further info about f and m.

Now, but both equations together and you have a system of two unknowns and two equations, easily solvable:
m + f = 4 000
3m + 5f = 15 000.

So C is indeed correct.
Top
Master | Next Rank: 500 Posts
Posts: 122
Joined: Mon Dec 15, 2008 12:03 am
Thanked: 2 times

by vkb16 » Tue Feb 17, 2009 8:58 pm
thanks a lot!
Top
Post new topic Post Reply
• Page 1 of 1