Is it just me or this problem written very poorly?

[NathanielJ.Ho]

This problem confused me greatly because I thought it was saying x times y is a 2 digit number. It actually refers to x and y as the tens and units places in a two digit number.

Question: If xy represents a positive two-digit number, where x and y are single digit integers, which of the following CANNOT be true?
A x + y = 9
B xy = 9
C x - y = 9
D y - x = 9
E x/y = 9

Solution explanation:
Try to find at least one pair of values for x and y that could work for each answer choice. This is possible for all answer choices except choice D.

(A) x + y = 9
x = 4, y = 5
(B) xy = 9
x = 1, y = 9
(C) x - y = 9
x = 9, y = 0
(D) y - x = 9
x = ..., y = ...
(E) x/y = 9
x = 9, y = 1

There are no possible values for x and y that could satisfy the equation y - x = 9. The greatest possible value for x and y is 9, but the smallest value for x is 1 whereas y can be 0. (If x = 0, then xy represents a single digit number, for example 08, which equals 8).

The correct answer is D.

[camille.lambert]

Probably in the sentence "xy REPRESENTS a 2 digit number" x is the tenths and y the unit digit, otherwise it would maybe have been "xy IS a 2 digit number" or even clearer (lets hope will be so at the exam if it is the case) "x times y is a 2 digit number"

Interesting danger you're pointing out, because at the exam (with the stress going on) I dont know if I would have thought about that!

[Ben Ku]

Hi,

I agree that this question is easily mis-interpreted. Whenever you have a question where the word "digit" shows up, consider thinking about place values instead of operations. Hope that helps.