GMAT Club Around The World!!! If positive integers x and y are not bot

Question

If positive integers x and y are not both even, which of the following must be odd?

A. x/y

B. 3xy

C. 2xy - 1

D. x + y

E. x - y

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Nipungupta9081 · Answer

IMO C

any Integer multiplied by even Integer gives Even

2 * even * odd - 1 = ODD
2 * even * even - 1 = ODD

Posted from my mobile device

Deepakjhamb · Answer

If positive integers x and y are not both even, which of the following must be odd?

A. x/y

B. 3xy

C. 2xy - 1

D. x + y

E. x - y

not both even means 1 is odd and other is even or both are odd this can also be the meaning

so definitely we have c ) 2xy -1 as the answer as it comes out to be e-o = o so its mbt

answer is c) 2xy-1

ananya3 · Answer

IMO C

x>0, y>0
x and y not both even
case 1: x=even, y=odd
case 2: x=odd, y = even
case 3: x=odd, y=odd

A. x/y 
for case 1: even/odd = may be even integer or decimal
eg: x=6, y=3 x/y = 2
for case 2: x/y = odd/even - not an integer

B. 3xy 
for case1 and case2 - 3*even*odd = even

C. 2xy - 1
for all cases 2*number = even
even -1 (odd) = odd
  Correct

D. x + y
for case 3: odd + odd = even

E. x - y
for case 3: odd - odd = even

rocky620 · Answer

Either one will be odd or both will be odd

A. x/y : 12/3 = 4.  Eliminate

B. 3xy : 3*2*1 = 6  Eliminate

C. 2xy - 1: irrespective of the values of x&y, 2xy will be even, so even-odd = odd. Correct

D. x + y: can be odd/even.  Eliminate

E. x - y: can be odd/even.  Eliminate

IMO Option C

Neha2404 · Answer

Imo-C

Either x or y is even or both are odd integer 
2xy-1
Even*odd*odd =even
Or 
Even*even*even= even
And 
Even -1 = odd

Posted from my mobile device

TarunKumar1234 · Answer

given, positive integers x and y are not both even, So, x, y can be (odd,odd), (even,odd) or (odd,even).

A. x/y -> Not sure, if integer.
B. 3xy -> Not always odd.
C. 2xy - 1 -> even-odd= odd always.
D. x + y -> odd +odd = even, Not always odd.
E. x - y ->odd -odd = even, Not always odd.

So, I think C.

BIDJI23 · Answer

2 possibilities

1 is even and the other odd
2 are odds

2xy is even whatever x and y are. So an even number minus 1 is always odd

PUSH C

Green2k1 · Answer

Correct Answer C

If positive integers x and y are not both even, which of the following must be odd?
Means 
 x----------Y
odd------odd
Even-----odd
odd (O)-------Even(E)

A. x/y
 -Maybe a fraction

B. 3xy
 3 *O*O =O
3 *E*O =E
3 *O*E =E

C. 2xy - 1
 2 *O*O -O =O
2 *E*O -O =O
2 *O*E -O =O

D. x + y
 O+O =E
E+O =O
O+E =O
 
E. x - y
 O-O =E
E-O =O
O-E =O

manasi05 · Answer

We are given,
x and y are positive integers
They are not both even so they can be either even or odd or they can both be odd. Now lets evaluate the answer choices:
A. x/y will be odd if both x and y are odd and even if they are odd-even number pair
B. 3xy will be odd if both x and y are odd, and even if they are odd-even number pair
C. 2xy - 1 will be always odd because 2xy will be always even and subtracting an odd number from even number gives odd number.
D. x + y will be even if both x and y are odd and odd if they are odd-even number pair
E. x-y will be even if both x and y are odd and odd if they are odd-even number pair

Hence the answer will be C

GMAT Club Around The World!!! If positive integers x and y are not bot

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