Multiple choice general knowledge math & puzzles

The average between a two digit number and the number obtained by interchanging the digits is 9. What is the difference between the two digits of the number?

  1. 8

  2. 2

  3. 5

  4. Cannot be determined
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let the number be 10x + y. The reversed is 10y + x. Average: [(10x+y) + (10y+x)]/2 = 9, so 11(x+y) = 18. Since x and y must be integers, no such two-digit number exists. Thus, it cannot be determined.

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