Is ab+c an odd integer, if a, b and c are positive integers? (1) c is

Question

Is ab+c an odd integer, if a, b and c are positive integers?

(1) c is odd.
(2) Only one of the integers is even

New question

PKN · Answer

Given, a,b, and c are positive integers.
Question stem:-Is ab+c an odd integer?
st1:- c is odd

So, when ab=Even , ab+c=Even+odd=Odd
but, when ab=Odd, ab+c=Odd+odd=Even

So, insufficient.

st2:-Only one of the integers is even
when a=even & b,c=odd; ab+c=even+odd=odd
when b=even & a,c=odd; ab+c=even+odd=odd
when c=even & a,b=odd; ab+c=odd+even=odd
So, sufficient.

Ans. (B)

GyMrAT · Answer

a,b,c > 0

Is (ab + c) - odd ?

If ab - odd & c - even, then (ab + c) - odd
If ab - even & c - odd, then (ab + c) - odd

If ab - odd, then a - odd & b - odd
If ab - even, then a or b or both - even

Statement 1: c is odd

ab can be odd or even & hence (ab + c) can be even or odd.

Statement 1 alone is Not Sufficient.

Statement 2: Only one of a, b, c is even

If c - even, then ab - odd, hence (ab + c) - odd
If b - even, then ab - even & c - odd, hence (ab + c) - odd
If a - even, then ab - even & c - odd, hence (ab + c) - odd

Statement 2 is Sufficient.

Answer B.

Thanks,
GyM

anupam87 · Answer

1. Not sufficient. We do not know anything about a and b

2. a or b even - even + odd = odd 
 C even - odd + even = odd. 
Sufficient

Answer (B)

Posted from my mobile device

PKN · Answer

Hi  chetan2u ,
Kindly provide the OA. It still displays a question mark(?) in my error log.

Thanking you.

KSBGC · Answer

probable combination :

a = odd
b = odd
c = even

or

a = odd / even 
b = odd / even

c = odd.

Note: odd + even = odd

Statement 1 : c is odd. C could be odd . In this case ab has to be even. No information about a or b. NOT sufficient.

Statement 2 : Among the 3 integers 1 is even. It means rest of the 2 are odd. It can be calculated as follows:

If a = even , ab is even. C is odd. So, ab + c = odd.

If c = even , ab is odd. Even + odd = odd.

Sufficient.

Thus the best answer is B.

Is ab+c an odd integer, if a, b and c are positive integers? (1) c is

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Data Sufficiency (DS) Questions

Is ab+c an odd integer, if a, b and c are positive integers? (1) c is

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards