Sum of positive integers x and y is 72. What is xy?
a. x = y + 1
b. x and y have same tens digit
Sum of positive integers
This topic has expert replies
-
- Master | Next Rank: 500 Posts
- Posts: 424
- Joined: Sun Dec 07, 2008 5:15 pm
- Location: Sydney
- Thanked: 12 times
- DanaJ
- Site Admin
- Posts: 2567
- Joined: Thu Jan 01, 2009 10:05 am
- Thanked: 712 times
- Followed by:550 members
- GMAT Score:770
This problem is wrong.
Statement 1 doesn't make sense and let me explain why. x and y are both positive integers and it says there that x = y + 1. Since x + y = 72, then it's safe to say that y + 1 + y = 2y + 1 = 72. This means that 2y = 71, with y = 35.5. As you can see, 35.5 is NOT a positive integer. This contradicts the initial assumption.
Statement 1 doesn't make sense and let me explain why. x and y are both positive integers and it says there that x = y + 1. Since x + y = 72, then it's safe to say that y + 1 + y = 2y + 1 = 72. This means that 2y = 71, with y = 35.5. As you can see, 35.5 is NOT a positive integer. This contradicts the initial assumption.
GMAT/MBA Expert
- Ian Stewart
- GMAT Instructor
- Posts: 2621
- Joined: Mon Jun 02, 2008 3:17 am
- Location: Montreal
- Thanked: 1090 times
- Followed by:355 members
- GMAT Score:780
Agree with Dana - if x+y = 72, then either x and y are both odd, or x and y are both even. Statement 1 says that x and y are consecutive integers (i.e. one of them is odd, the other even) which contradicts information in the question.piyush_nitt wrote:Sum of positive integers x and y is 72. What is xy?
a. x = y + 1
b. x and y have same tens digit
If S1 didn't lead to a contradiction (e.g. if it said x = y+2), using it and the information in the question, you'd be able to find both x and y, and therefore answer the question. S2 alone would not be sufficient, since there are a few pairs of values of x and y with the same tens digit that add to 72 (36+36, 35+37, etc), and for each we get a different product xy.
Still, if that's the original version of the question, there's something wrong with the source.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com
ianstewartgmat.com
ianstewartgmat.com