Consecutive integers

This topic has expert replies
Source: — Problem Solving |

User avatar
Legendary Member
Posts: 1100
Joined: Sat May 10, 2014 11:34 pm
Location: New Delhi, India
Thanked: 205 times
Followed by:24 members

by GMATinsight » Fri Sep 05, 2014 10:35 pm
j_shreyans wrote:What is the product of three consecutive integers?

(1) At least one of the integers is positive.

(2) The sum of the integers is less than 6.

OAC
Question : Product of 3 consecutive integers = ???

Statement 1) At least one of the integers is positive.

then, Number could be -1, 0, 1 and they could also be 1, 2, 3 giving us different results therefore
INSUFFICIENT

Statement 2) The sum of the integers is less than 6.
For this to be true the set of 3 consecutive integers be {0, 1, 2} or {-1, 0, 1} or {-3, -2, -1}
Therefore product of three consecutive integers could be 0 or 0 or -6 respectively [Inconsistent]
INSUFFICIENT

Combining the two statements
The only sets that are possible are {0, 1, 2} and {-1, 0, 1} as atleast one of the numbers must be positive
but the product of all three is always zero, therefore
SUFFICIENT

Answer: Option C
"GMATinsight"Bhoopendra Singh & Sushma Jha
Most Comprehensive and Affordable Video Course 2000+ CONCEPT Videos and Video Solutions
Whatsapp/Mobile: +91-9999687183 l [email protected]
Contact for One-on-One FREE ONLINE DEMO Class Call/e-mail
Most Efficient and affordable One-On-One Private tutoring fee - US$40-50 per hour

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sat Sep 06, 2014 6:45 am
j_shreyans wrote:What is the product of three consecutive integers?

(1) At least one of the integers is positive.
(2) The sum of the integers is less than 6.
Target question: What is the product of three consecutive integers?

Statement 1: At least one of the integers is positive.
There are several sets of consecutive integers that satisfy this condition. Here are two:
Case a: the numbers are 1, 2 and 3, in which case their product is 6
Case b: the numbers are 2, 3 and 4, in which case their product is 24
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: The sum of the integers is less than 6.
There are several sets of consecutive integers that satisfy this condition. Here are two:
Case a: the numbers are -3, -2 and -1, in which case their product is -6
Case b: the numbers are 0, 1 and 2, in which case their product is 0
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 2 tells us that the sum of the integers is less than 6
Notice that the three consecutive integers 1, 2 and 3 have a sum of 6.
This tells us that the greatest of the three integers is LESS than 3

Statement 1 tells us that at least one of the integers is positive.

There are only 2 possible cases that satisfy both statements. They are:
Case a: the numbers are 0, 1 and 2 in which case their product is 0
Case b: the numbers are -1, 0 and 1, in which case their product is 0

IMPORTANT: Although we can't be certain whether the three numbers are {0,1,2} or {-1,0,1}, the answer to the target question is THE SAME for both cases.
In other words, we can be CERTAIN that the product of the three integers is 0
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image

GMAT Instructor
Posts: 2630
Joined: Wed Sep 12, 2012 3:32 pm
Location: East Bay all the way
Thanked: 625 times
Followed by:119 members
GMAT Score:780

by Matt@VeritasPrep » Sat Sep 06, 2014 8:59 am
Here's one more quick approach:

S1 tells us the set is anything from {-1, 0, 1} to {infinity, infinity + 1, infinity + 2}. So the product could be all sorts of things; INSUFFICIENT.

S2 tells us the set is anything from {-infinity -2, -infinity -1, -infinity} to {0, 1, 2}. Again, INSUFFICIENT.

Taking the two together, the only sets we have are {-1, 0, 1} and {0, 1, 2}. (Anything BIGGER, such as {1, 2, 3}, violates S2, while anything SMALLER, such as {-2, -1, 0}, violates S1.)

In both cases the product is 0, so the two statements together are SUFFICIENT!