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

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AFCAT 11th Aug 2024 (Shift 1) Memory Based Paper.
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  1. 3
  2. 2
  3. 4
  4. 1

Answer (Detailed Solution Below)

Option 4 : 1
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AFCAT 16th Feb 2024 (Shift 1) Memory Based Paper.
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Detailed Solution

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Given:

The difference between a two-digit number and the number obtained by interchanging its digits is 9.

Formula used:

Let the two-digit number be 10x + y, where x is the tens digit and y is the units digit.

The number obtained by interchanging the digits is 10y + x.

Difference = (10x + y) - (10y + x) = 9

Difference between two digits = |x - y|

Calculation:

(10x + y) - (10y + x) = 9

⇒ 10x + y - 10y - x = 9

⇒ 9x - 9y = 9

⇒ 9(x - y) = 9

⇒ x - y = 1

⇒ Difference between two digits = |x - y| = 1

∴ The correct answer is option (4).

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