Hi,
This is a perfect example for trap question in GMAT.
Already someone has figured the trap.
Answer choice B would have been the obvious trap answer. Whenever anything look too obvious it’s better to cross check, may not every time it would be a trap answer, but it’s always better to have a another look at it.
I will give my 2 – cents to this question.
Question: Is A*B is even?
That is product of two numbers is it even?
Note that we don’t know anything about A and B,
These below three rules of addition and multiplication of integers will help.
Add or sub :Even + even = Even
Even + Odd = Odd
Odd + Odd = Even
Multiplication:Odd * odd = odd
Even * odd = even
Even * even = even.
So let’s get into the statements,
Statement I is insufficient:
A + B = 7
First of all here A + B is 7, with this we can’t really say whether A and B are integers,
Maybe here,
A = 3.5 and B = 3.5
Or it could be
A= 3 and B = 4.
So insufficient.
Statement II is insufficient.
B is even,
Here is where someone has to careful because it’s easy to fall for the trap here, because B is even then AB is even.
Note that: This is possible only when A and B is even.
We can get that B is an integer, but not really sure about A.
It could be,
A = ½ and B = 2, answer to the question would be NO.
Or
A = ½ and B = 4, Answer to the question would be YES.
Together it is sufficient,
A+B = 7,
Since B is even, A has to be odd to get the sum as odd integer.
So AB is even.
So together it is sufficient.
Answer is C.
Hope this helps
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