Oct 16 08:00 PM PDT  09:00 PM PDT EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299) Oct 19 07:00 AM PDT  09:00 AM PDT Does GMAT RC seem like an uphill battle? eGMAT is conducting a free webinar to help you learn reading strategies that can enable you to solve 700+ level RC questions with at least 90% accuracy in less than 10 days. Sat., Oct 19th at 7 am PDT Oct 20 07:00 AM PDT  09:00 AM PDT Get personalized insights on how to achieve your Target Quant Score. Oct 22 08:00 PM PDT  09:00 PM PDT On Demand for $79. For a score of 4951 (from current actual score of 40+) AllInOne Standard & 700+ Level Questions (150 questions)
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 58400

If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
06 Dec 2016, 07:25
Question Stats:
83% (01:12) correct 17% (01:16) wrong based on 129 sessions
HideShow timer Statistics
If a and b are positive integers, is a + b even? (1) 5a – 1 is odd (2) ab is even
Official Answer and Stats are available only to registered users. Register/ Login.
_________________



Senior Manager
Joined: 24 Oct 2016
Posts: 251
Location: India
Concentration: Finance, International Business
GPA: 3.96
WE: Human Resources (Retail Banking)

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
06 Dec 2016, 07:36
E the value of a can be odd or even but we can't specify the vale of b it can be odd or even too



Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4773
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
06 Dec 2016, 11:36
Bunuel wrote: If a and b are positive integers, is a + b even? (1) 5a – 1 is odd (2) ab is even FROM STATEMENT  I ( INSUFFICIENT )5a  1 = Odd ; So, a must be Odd We do not know , the value of b so we can not comment on the value of a + b FROM STATEMENT  II ( INSUFFICIENT )ab = Even We can have 3 Possibilities  1. Both a and b are even 2. a is even & a is odd 3. b is even & a is Odd FROM STATEMENT  I & II ( INSUFFICIENT )Since we do not have a unique value of b , this statement is insufficient... Thus, Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed, asnwer will be (E)
_________________



Intern
Joined: 09 Dec 2013
Posts: 4

If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
09 Mar 2017, 21:52
FROM STATEMENT  I ( INSUFFICIENT )
5a  1 = Odd 5a=even (as odd+1=even) a=even/5 = even
We do not know the value of b so we can not comment on the value of a + b
FROM STATEMENT  II ( INSUFFICIENT )
ab = Even
We can have 3 Possibilities 
1. Both a and b are even 2. a is even & a is odd 3. b is even & a is Odd
FROM STATEMENT  I & II ( SUFFICIENT )
from statement I we know a=even & From statement II b=even/even=even
Hence a=even and b=even even + even = even
Answer should be C (Together both statements are sufficient to answer)



Director
Status: Come! Fall in Love with Learning!
Joined: 05 Jan 2017
Posts: 533
Location: India

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
10 Mar 2017, 02:47
St 1: 5a1 is odd or 5a is even or a is even. Nothing can be said about b. INSUFFICIENT St 2: ab is even. that menas either a or b or both are even.INSUFFICIENT St 1 & St 2: a is even. b can be even or odd. hence a +b can be even or odd. INSUFFICIENT Option E
_________________
GMAT Mentors



Current Student
Joined: 19 Aug 2016
Posts: 146
Location: India
GPA: 3.82

If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
20 Jun 2017, 04:49
Abhishek009 wrote: Bunuel wrote: If a and b are positive integers, is a + b even? (1) 5a – 1 is odd (2) ab is even FROM STATEMENT  I ( INSUFFICIENT )5a  1 = Odd ; So, a must be Odd We do not know , the value of b so we can not comment on the value of a + b Hi, I think from statement 1 it is clear that a is even, and not odd. since 5 multiplied with an even number will result in a number ending with 0 which in turn will give an odd number after subtracting 1.
_________________
Consider giving me Kudos if you find my posts useful, challenging and helpful!



Manager
Joined: 05 Nov 2014
Posts: 103
Location: India
Concentration: Strategy, Operations
GPA: 3.75

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
20 Jun 2017, 07:02
If a and b are positive integers, is a + b even?
(1) 5a – 1 is odd (2) ab is even
Statement 1 : 5a1=odd, Rewrite this equation. 5a=odd+1, 5a=even.So a=even. This is insufficient to compute the value of a+b. Statement 2: ab= even . 3 cases are possible. 1.a=even b=odd 2.a=odd b=even 3.a=even b=even.
Combine st1 and st2 We still have 2 choices 1 &3 from st 2 as we know a to be even from st1
Therefore the answer is E.



Senior PS Moderator
Joined: 26 Feb 2016
Posts: 3341
Location: India
GPA: 3.12

If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
20 Jun 2017, 10:37
(1) 5a – 1 is oddThis is possible only when a is even. However we have no information about b, which could be either odd or even. If b is odd, a+b is not even whereas b being even means a+b is even Insufficient. (2) ab is evenThis statement is true when : 1.a,b are both even 2.a is odd, b is even 3.a is even, b is odd. Using condition1, a+b is even. However using condition2 and 3, a+b is odd. Insufficient. Combining both the statements, a being even and b being odd, makes a+b odd. On the contrary, b being even makes a+b even. Hence, insufficient(Option E)
_________________
You've got what it takes, but it will take everything you've got



Target Test Prep Representative
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2816

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
06 Jul 2017, 17:54
Bunuel wrote: If a and b are positive integers, is a + b even? (1) 5a – 1 is odd (2) ab is even We need to determine whether a + b is even, or whether a and b are both even or both odd. Statement One Alone: 5a – 1 is odd Since 5a  1 is odd, a must be even. Here’s why: 5a  1 = odd 5a = odd + 1 5a = even Since adding 1 to any odd number gives us an even number, we know that 5a must be even. The only way for this to happen is if a is even. (Recall that odd x even = even.) However, since we do not know anything about b, statement one alone is not sufficient to answer the question. Statement Two Alone: ab is even Recall that even x even = even OR even x odd = even. Since ab is even, a and b could both be even OR one value could be even and the other odd. Thus, we cannot determine whether a + b is even. Statement two alone is not sufficient to answer the question. Statements One and Two Together: Using statements one and two, we still do not have enough information to determine whether a + b is even. We know that a is even, but we still cannot determine whether b is even. If a is even and b is even, then a + b is even. However, if a is even and b is odd, then a + b is odd. Answer: E
_________________
5star rated online GMAT quant self study course See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews
If you find one of my posts helpful, please take a moment to click on the "Kudos" button.



Retired Moderator
Joined: 19 Mar 2014
Posts: 922
Location: India
Concentration: Finance, Entrepreneurship
GPA: 3.5

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
11 Jul 2017, 07:46
Bunuel wrote: If a and b are positive integers, is a + b even? (1) 5a – 1 is odd (2) ab is even If a and b are positive integers, is a + b even?(1) 5a – 1 is oddThis tells us that a is even. Let's check how: 5a  1 = Odd 5a = Odd + 1 5a = Even As, 5 * Even = Even a is EVENWith this we cannot determine if a and be is even as we do not know if b is even or odd. Hence, (1) ===== is NOT SUFFICIENT(2) ab is eventhis is only possible when: a  Even and b  Even a  Odd and b  Even a  Even and b  Odd based on above scenarios a and b can be even or odd and hence not sufficient to determine if a + b is even Hence, (2) ===== is NOT SUFFICIENTCombining (1) & (2) after combining we come to know that a will be even however, we are not sure on the value of b, b can either be odd or it can be even. Hence we are still not able to determine if a + b = even Hence, (1) & (2) ===== is NOT SUFFICIENT.Hence, Answer is AYou liked the answer? Appreciate with a Kudos
_________________
"Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent."
Best AWA Template: https://gmatclub.com/forum/howtoget60awamyguide64327.html#p470475



Manager
Joined: 05 Nov 2014
Posts: 103
Location: India
Concentration: Strategy, Operations
GPA: 3.75

Re: If a and b are positive integers, is a + b even?
[#permalink]
Show Tags
11 Jul 2017, 09:23
I think the answer is E because from statement 1 we know that a is even and we have no information about b. And from statement 2, we know either a or b is even or both are even. So even after combining b can be even or odd. So the answer is option E Sent from my Lenovo K33a42 using GMAT Club Forum mobile app




Re: If a and b are positive integers, is a + b even?
[#permalink]
11 Jul 2017, 09:23






