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

Redeem

Integer

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 41
Joined: Tue Dec 16, 2008 11:53 pm

Integer

by billyr » Wed Feb 25, 2009 10:14 pm
A certain list consist of several different integer. Is the product of all integer in the list is positive?

(1) The product of the greatest and smallest in the list is positive
(2) There is an even number of integer in the list

The answer is c(need both statement), but why c?

Thanks
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 » Wed Feb 25, 2009 11:10 pm
Here's how I see it:
1. tells us that (smallest)*(greatest) is positive means that:
a. both are positive and since they are the "ends" of the series, that makes all the numbers positive. In this case, the product will be positive
b. both are negative, making all of the numbers negative. However, in this case we cannot tell if the product is positive, since we don't know if we have an even or an odd "number" of numbers. Take for example: -5, -4, -3. While it's true that (-5)*(-3) is positive, that cannot be said about the product of the three.

2 doesn't help much. All numbers could be positive, or you could have smth like: -5, 3, 4, 5.

Put the two together and you "eliminate" that weak spot in case b from stmt 1: even if all numbers are negative, they "cancel" each other's minuses. So the OA is ok.
Top
Master | Next Rank: 500 Posts
Posts: 160
Joined: Fri Aug 22, 2008 4:54 am
Thanked: 5 times
GMAT Score:660

by crazy4gmat » Thu Feb 26, 2009 9:53 am
gr8 expln. :)
Top
Post new topic Post Reply
• Page 1 of 1