Each stmt by itself is obviously insufficient, since we need to know info about both x and y to solve the problem. Now, take them both together:
1. -x < 8/9 makes x > -8/9
2. -y < 1/8 makes y > -1/8
Now, as you can see, this info is not enough as well. Consider x = y = 0: this means that indeed x + y < 1. But, if you take say x = 2 and y = 1, then x + y > 1.
This is why the OA is E
BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Featured Course
Target Test Prep GMAT OnDemand
Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.
- 715+ score guarantee — highest in the industry (99th percentile)
- 52 chapters · 1,500+ lessons · 4,000+ practice questions
- 400 hours of video · 1,500+ instructor-led HD smartboard lessons
- 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
- 24/7 live support + weekly Zoom office hours with GMAT instructors
- TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
- 1,200+ flashcards + AI-powered study assistant & daily calendar
- OnDemand, LiveTeach & GMAT Bootcamp formats available
- Also: GRE, SAT Math & Executive Assessment courses
- MBA Admissions Consulting now available
- 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
- 200,000+ students served
- 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★
5.0
(559 reviews)
130-pt guarantee
$0 to start
then $127/mo
Is x + y < 1 ?
Source: Beat The GMAT — Data Sufficiency |
When you multiply an inequality by a negative number, the sense of the inequality is reversed. For example, take " x < 1 ". Multiply by -1, and reverse the sense to get " -x > -1 ", not " -x < -1 ".
(1) subtract 1, and multiply by -1 to get
x > 1/9
(2) subtract 2, and multipy by -1 to get
y > 15/8
I think they're sufficient together. What is the source? Perhaps there's a typo in the question or your posting?
(1) subtract 1, and multiply by -1 to get
x > 1/9
(2) subtract 2, and multipy by -1 to get
y > 15/8
I think they're sufficient together. What is the source? Perhaps there's a typo in the question or your posting?
Want more practice GMAT questions? check out
https://www.testsandtutors.com/course/view.php/GMAT
https://www.testsandtutors.com/course/view.php/GMAT
Hah, I read the (1) and (2) in the question as part of the equations.
Pretend I said what DanaJ said.
Moving right along....
Pretend I said what DanaJ said.
Moving right along....
Want more practice GMAT questions? check out
https://www.testsandtutors.com/course/view.php/GMAT
https://www.testsandtutors.com/course/view.php/GMAT
Hi DanaJ, its not -x.
I have edited the ques, the hyphen was misconstrued as -ve sign
I have edited the ques, the hyphen was misconstrued as -ve sign
DanaJ wrote:Each stmt by itself is obviously insufficient, since we need to know info about both x and y to solve the problem. Now, take them both together:
1. -x < 8/9 makes x > -8/9
2. -y < 1/8 makes y > -1/8
Now, as you can see, this info is not enough as well. Consider x = y = 0: this means that indeed x + y < 1. But, if you take say x = 2 and y = 1, then x + y > 1.
This is why the OA is E
OK then, let's look at it again:
So you have that x < 8/9 and y < 1/8. The trick here is to notice that y is smaller than 1/8 INSTEAD of 1/9. If you had that:
x < 8/9
y < 1/9
--------
x + y would indeed be smaller than 1.
But since 1/8 > 1/9, you get that there is a small chance that y might be in that interval between 1/9 and 1/8. Look at this:
x < 8/9
y < 1/8
--------
x + y < 8/9 + 1/8 or x + y < 73/72.
It's that small portion of (73/72 - 1) = 1/72 that gives you the headache.
This is why I'm sticking by my answer.
So you have that x < 8/9 and y < 1/8. The trick here is to notice that y is smaller than 1/8 INSTEAD of 1/9. If you had that:
x < 8/9
y < 1/9
--------
x + y would indeed be smaller than 1.
But since 1/8 > 1/9, you get that there is a small chance that y might be in that interval between 1/9 and 1/8. Look at this:
x < 8/9
y < 1/8
--------
x + y < 8/9 + 1/8 or x + y < 73/72.
It's that small portion of (73/72 - 1) = 1/72 that gives you the headache.
This is why I'm sticking by my answer.
it is easier to convert it into decimals and then solve
x < 8/9 ~0.888
y < 1/8 ~0.125
Case I: now lets suppose x = 0.887 and y = 0.124
x +y = 1.011 >1
Case I: now lets suppose x = 0.6 and y = 0.1
x +y = 0.7 <1
Hence the answer should be E
x < 8/9 ~0.888
y < 1/8 ~0.125
Case I: now lets suppose x = 0.887 and y = 0.124
x +y = 1.011 >1
Case I: now lets suppose x = 0.6 and y = 0.1
x +y = 0.7 <1
Hence the answer should be E
SACX
Lets plug in values,asht wrote:Is x + y < 1 ?
1. x < 8/9
2. y < 1/8
I answered C, but unfortunately it was shown as wrong. The given OA answer didn't make any sense to me. Pls help!
OA is E
1) X should be 0.888888888888887 or lesser
2) Y should be 0.1025 or lesser
1+2) x+y = 1.013, which is greater than 1 (max value)
1+2) x+y = 0.001+0.001 = 0.002, which is less than 1
So insufficient!
IMO:E
