xy=10^nBrent Hanneson wrote:x and y are positive integers such that xy = 10^n. If x>y, the units digit of x-y CANNOT be
A) 1
B) 3
C) 5
D) 7
E) 9
x=200, y=5, x-y = 195. so not 5parallel_chase wrote:xy=10^nBrent Hanneson wrote:x and y are positive integers such that xy = 10^n. If x>y, the units digit of x-y CANNOT be
A) 1
B) 3
C) 5
D) 7
E) 9
x>y
x =5 , y= 2 , x-y = 3
x = 25, y = 4, x-y = 1
x = 10, y = 1, x-y = 9
x = 25, y = 8, x-y = 7
Hence 5.
aroon7 wrote:x=200, y=5, x-y = 195. so not 5parallel_chase wrote:xy=10^nBrent Hanneson wrote:x and y are positive integers such that xy = 10^n. If x>y, the units digit of x-y CANNOT be
A) 1
B) 3
C) 5
D) 7
E) 9
x>y
x =5 , y= 2 , x-y = 3
x = 25, y = 4, x-y = 1
x = 10, y = 1, x-y = 9
x = 25, y = 8, x-y = 7
Hence 5.
Ans is 7
when x= 25, y=8, we get xy = 200. this is not nth power of 10...
what is the OA?
thanks!
I hope these 2 questions dont stop you from drafting questions in futureBrent Hanneson wrote:Man, what a bad day for me.
I think this might be my last post, since I have now posted 2 questions with missing/incorrect information.
The question needs the proviso, "x and y" are not multiples of 10.
If we add that proviso, the correct answer is C (5).
Yikes - pretty sloppy stuff.
Sorry to all those who spent a great deal of time on this poorly-constructed question.
I hope not- it's clear that many people here have appreciated your questions, and I think everyone here understands that designing questions can be a tricky thing to do, especially when a question doesn't follow a pre-existing model. One of the more interesting facts that I found reading the legal documents from the GMAC/ScoreTop lawsuit: to design one official GMAT question, GMAC spends, on average, $2400, which should give people some idea of how much work goes into this (and why it's so hard to emulate the real thing).Brent Hanneson wrote:Man, what a bad day for me.
I think this might be my last post
As a suggestion, it might be more elegant to say that the GCD of x and y is 1, rather than to say that neither is a multiple of 10. It's a nice question, just as long as some kind of condition is added.Brent Hanneson wrote: The question needs the proviso, "x and y" are not multiples of 10.
If we add that proviso, the correct answer is C (5).
