-
GMATCRUSHER
- Junior | Next Rank: 30 Posts
- Posts: 14
- Joined: Sat Oct 11, 2008 2:43 pm
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
integers
Source: Beat The GMAT — Problem Solving |
Set up a table with three columns, and see which combinations of r and s result in an odd integer for rs+r :
r s rs+r
O O E (OxO+O = O+O = E)
O E O (OxE+O = E+O = O)
E O E (ExO+E = E+E = E)
We don't need to check r (E), s (E) combination, but if you want you can.
So rs+r would be odd only when r is odd and s is even. Plug this combination in the answer choices and see which one results in an even integer. Only the 2nd one (i.e. s) does.[/u]
r s rs+r
O O E (OxO+O = O+O = E)
O E O (OxE+O = E+O = O)
E O E (ExO+E = E+E = E)
We don't need to check r (E), s (E) combination, but if you want you can.
So rs+r would be odd only when r is odd and s is even. Plug this combination in the answer choices and see which one results in an even integer. Only the 2nd one (i.e. s) does.[/u]
imo b .. s
rs + r --> odd --> r(s+1) --> odd
say r = odd --> s+1 --> odd --> s - even
r(s+1) --> odd
say r = even --> s+ 1 --> odd --> not possible...
both r and s+1 have to be odd for the expression to be odd....
if s+ 1 is odd then we have s as even
rs + r --> odd --> r(s+1) --> odd
say r = odd --> s+1 --> odd --> s - even
r(s+1) --> odd
say r = even --> s+ 1 --> odd --> not possible...
both r and s+1 have to be odd for the expression to be odd....
if s+ 1 is odd then we have s as even
