If AB represents a positive two digit number, where A and B are single digit integers, which of the following cannot be true?
A) A+B =9
C) A-B = 9
D) B-A= 9
E) A/B = 9
I'll solve this by showing counterexamples for four of the answer ----
(A) AB = 45 or 63 or 27
(B) AB = 33 or 19
(E) AB = 91
(D) is impossible because 09 is not a valid two digit number --- if there's a zero in the ten's place, that's just 9, a single digit number. Therefore, no valid two digit number would satisfy (D).
Let me know if anyone reading this has questions on anything I have said.
Magoosh Test Prep