OG 2016 #87 PS

Expert replies

Azizakaria: Senior | Next Rank: 100 Posts; Posts: 76; Joined: Sat Sep 29, 2012 11:19 am; Thanked: 3 times

by Azizakaria » Fri Oct 09, 2015 9:41 am

87. The sum of all the integers k such that âˆ’26 < k < 24 is
(A) 0
(B) âˆ’2
(C) âˆ’25
(D) âˆ’49
(E) âˆ’51

i don't understand why the answer is D

Like this post

Source: Beat The GMAT — Problem Solving | Fri Oct 09, 2015 9:41 am

GMAT/MBA Expert

[email protected]: Elite Legendary Member; Posts: 10392; Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members; Location: Palo Alto, CA; Thanked: 2867 times; GMAT Score:800

by [email protected] » Fri Oct 09, 2015 9:47 am

Hi Azizakaria,

We're limited to the INTEGERS that fall in the range -26 < K < 24....so that would be....

-25, -24, -23.....0.....22, 23

Each of the positive integers form 1 to 23 (inclusive) would be 'cancelled out' by the negative integers from -1 to -23 (inclusive). The sum of ALL of those terms would be 0. But then you have to consider the other remaining integers: -24 and -25. Adding those two numbers gets us -49.

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

Like this post

GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Fri Oct 09, 2015 9:51 am

Azizakaria wrote:87. The sum of all the integers k such that âˆ’26 < k < 24 is
(A) 0
(B) âˆ’2
(C) âˆ’25
(D) âˆ’49
(E) âˆ’51

i don't understand why the answer is D

(-25) + (-24) + (-23) + (-22) + (-21) + . . . . .+ 21 + 22 + 23

Notice that the blue values all cancel out, because for each positive value, there's a negative value with the same magnitude (e.g., -23 + 23 = 0, and -22 + 22 = 0, etc)

So, we're left with (-25) + (-24), which equals -49

Brent Hanneson - Creator of GMATPrepNow.com

Like this post

Azizakaria: Senior | Next Rank: 100 Posts; Posts: 76; Joined: Sat Sep 29, 2012 11:19 am; Thanked: 3 times

by Azizakaria » Sat Oct 10, 2015 2:44 am

now I understand, thanks for your help, the explanation in the OG is so unclear.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review