The average of nine 2-digit numbers is decreased by 6 when the digits of one of the 2-digit numbers is interchanged. Find the difference between the digits of that number.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 6
Let A denotes the average of given nine, 2-digit numbers.
Let 10x + y be the selected number out of given nine, 2-digit numbers; such that If the digits of the selected number are interchanged, then A decreased by 6.
⇒ {9A - (10x + y) + (10y + x)}/9 = A - 6
⇒ 9(x - y) = 54
⇒ x - y = 6