M16 Q18

Question

I think the ans should be E, as y =0 and x as odd integer case is not considered.

Guys input your explanations pls.

gurpreetsingh · Answer

Bump.... BB could u pls check this.

Bunuel · Answer

In case  x=odd  and  y=0  -->  2*x*5*y=0=even

Question:  2*x*5*y=even . As there is 2 as a multiple, then this expression will be even if  5xy=integer . Basically we are asked is  5xy=integer  true?

Note that  x  and  y  may not be integers for  2*x*5*y  to be even (example  x=\frac{7}{9}  and  y=\frac{9}{7} ) BUT if they are integers then  2*x*5*y  is even.

(1)  2+x+5+y=even  -->  7+x+y=even  -->  x+y=odd . Not sufficient. (x=1 and y=2 answer YES BUT x=1.3 and y=1.7 answer NO)

(2)  x-y=odd . Not sufficient. (x=1 and y=2 answer YES BUT x=1.3 and y=0.3 answer NO)

(1)+(2) Sum (1) and (2)  (x+y)+(x-y)=odd_1+odd_2  -->  2x=even  -->  x=integer  -->  y=integer  --> Both  x  and  y  are integers. Hence sufficient.

Answer: C.

M16 Q18

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