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Register now and save up to $200 Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code ## Operations with Rational Numbers tagged by: Brent@GMATPrepNow This topic has 4 expert replies and 0 member replies jmacym Newbie | Next Rank: 10 Posts Joined 29 Sep 2016 Posted: 6 messages #### Operations with Rational Numbers Sat Oct 08, 2016 10:42 am Elapsed Time: 00:00 • Lap #[LAPCOUNT] ([LAPTIME]) One of my review questions... The sum 7/8 + 1/9 is between... The correct answer is (B) 3/4 and 1 The explanation is as follows: Since 1/9 < 1/8, 7/8 + 1/9 < 7/8 + 1/8 = 1 answer choices C, D, and E can be eliminated. Since 7/8 > 6/8 = 3/4, 7/8 + 1/9 > 3/4 answer choice A can be eliminated. Thus, 3/4 < 7/8 + 1/9 < 1 Okay, so my thinking is first of all 7/8 + 1/9 is 71/72... obviously that was not even close to any of the answer choices. The explanation confuses me even more because it's saying 1/9 is less than 1/8...which I understand how and why that is true, but 1/9 could be less than TONS of numbers. How am I supposed to know to use 1/8 instead of, lets say, 1/7 or 1/6, 1/5..etc. to get to the correct answer? Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! ### GMAT/MBA Expert DavidG@VeritasPrep Legendary Member Joined 14 Jan 2015 Posted: 2301 messages Followed by: 115 members Thanked: 1074 times GMAT Score: 770 Sat Oct 08, 2016 10:49 am jmacym wrote: One of my review questions... The sum 7/8 + 1/9 is between... The correct answer is (B) 3/4 and 1 The explanation is as follows: Since 1/9 < 1/8, 7/8 + 1/9 < 7/8 + 1/8 = 1 answer choices C, D, and E can be eliminated. Since 7/8 > 6/8 = 3/4, 7/8 + 1/9 > 3/4 answer choice A can be eliminated. Thus, 3/4 < 7/8 + 1/9 < 1 Okay, so my thinking is first of all 7/8 + 1/9 is 71/72... obviously that was not even close to any of the answer choices. The explanation confuses me even more because it's saying 1/9 is less than 1/8...which I understand how and why that is true, but 1/9 could be less than TONS of numbers. How am I supposed to know to use 1/8 instead of, lets say, 1/7 or 1/6, 1/5..etc. to get to the correct answer? The idea is that (7/8) + (1/8) = 1. Because 1/9 < 1/8, it must be true that (7/8) + (1/9) < 1. (In essence, 1/8 was chosen because it allowed you to easily see how the sum would compare to one.) _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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Rich.C@EMPOWERgmat.com Elite Legendary Member
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Sat Oct 08, 2016 6:58 pm
Hi jmacym,

When posting a GMAT question, you should make sure to post the ENTIRE question (including the 5 answer choices). In many cases, the answer choices themselves provide a 'hint' as to how you can go about answering the question. The question that you're referring to includes the following answers:

The sum 7/8 + 1/9 is between?

A) 1/2 and 3/4
B) 3/4 and 1
C) 1 and 1 1/4
D) 1 1/4 and 1 1/2
E) 1 1/2 and 2

From the answer choices, we can see that there is no 'overlap' between any pair of consecutive answers, so we really just need to define the range. By extension, we likely do NOT need to do a perfect calculation to get to the correct answer (we can probably use a certain amount of estimation).

Since 6/8 = 3/4 = .75, we know that 7/8 has to be greater than .75 on its own.

7/8 + 1/8 would = 1, but since 1/9 < 1/8, then we're adding a number to .75 that will end up in a sum that is less than 1. We've now defined the range...

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### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
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Sat Oct 08, 2016 7:02 pm
jmacym wrote:
The sum 7/8 + 1/9 is between?

A) 1/2 and 3/4
B) 3/4 and 1
C) 1 and 1 1/4
D) 1 1/4 and 1 1/2
E) 1 1/2 and 2
7/8 + 1/8 = 1.
Since 1/9 is just a bit SMALLER than 1/8, 7/8 + 1/9 must be just a BIT LESS THAN 1.

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Brent@GMATPrepNow GMAT Instructor
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Sun Oct 09, 2016 7:25 am
Quote:
The sum 7/8 + 1/9 is between

A)1/2 and 3/4
B)3/4 and 1
C)1 and 1 1/4
D)1 1/4 and 1 1/2
E)1 1/2 and 2
Well, first we know that 7/8 + 1/8 = 1
Since 1/9 is a little bit less than 1/8, we know that the sum 7/8 + 1/9 will be a little bit less than 1.
Since 7/8 is also greater than 3/4, the answer must be B

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