If positive integers a and b are both odd, which of the following must

Question

If positive integers a and b are both odd, which of the following must not be odd?

A. ab
B. a(ab)
C. b – a – 1
D. (a + b)/2
E. a – b

stonecold · Answer

Odd -Odd => Even 
Hence E can never be even.

Hence E

prashantrchawla · Answer

If positive integers a and b are both odd. 
A. ab ----- Odd * Odd = Odd
B. a(ab)-- Odd * Odd * Odd = Odd
C. b – a – 1 -- Odd - Odd - 1 = Odd
D. (a + b)/2 -- Odd + Odd / 2 = Odd
E. a – b ---- Odd - Odd = Even in all the cases. Hence answer is E.

Abhishek009 · Answer

A. ODD * ODD = ODD

B. ODD(ODD*ODD) = ODD

C. ODD - ODD = EVEN - 1 = ODD

D. ODD + ODD = EVEN/2 = EVEN/ODD

E. ODD - ODD = EVEN

So, Correct answer will be (E)

RR88 · Answer

Option E

a & b are Odd integers. Odd: O, Even: E & Fraction: F.

A. ab = O*O = O
B. a(ab) = O(O*O) = O
C. b – a – 1 = O - O - 1 = E - 1 = O
D. (a + b)/2 = (O + O)/2 = E/2 = O
E. a – b = O - O = E

Seeker2802 · Answer

A. o1*o2=o
B. o1(o1*o2)=o
C. o2-o1-1=o
D. (o1+o2)/2=o
 E. o1-o2=e

Hence E

Yoohanna · Answer

How come D is not the answer if we apply 3+5/2=4 , therefore even?

Abhishek009 · Answer

Good observation, thats why I mentioned the result of (D) may/may not be EVEN

You have considered the numbers as 3 and 5 , see if I take the numbers as 1 and 5

\frac{(a + b)}{2} = \frac{6}{2} = 3 (ODD) 
  
Thus, (D) may/may not be even...

EMPOWERgmatRichC · Answer

Hi All,

This question can be approached with Number Property rules. We're told that A and B are both ODD, POSITIVE INTEGERS. We're asked which of the following MUST NOT be odd.

Answer A: (A)(B) = (odd)(odd) = odd 
Answer B: (A)(A)(B) = (odd)(odd)(odd) = odd 
Answer C: B - A - 1 = (odd) - (odd) - (odd) = odd 
Answer D: (A+ B)/2 = (odd + odd)/2 = (even)/2 = COULD be even (re: 4/2 = 2) OR odd (re: 6/2 = 3) 
Answer E: A - B = (odd) - (odd) = EVEN

There's only one answer that can NEVER be odd.

Final Answer:  E

GMAT assassins aren't born, they're made, 
Rich

ScottTargetTestPrep · Answer

Since odd - odd = even, answer choice E, a - b is not odd.

Answer: E

bumpbot · Answer

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If positive integers a and b are both odd, which of the following must

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If positive integers a and b are both odd, which of the following must

Prep Toolkit

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