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Difficulty: 3/102023 NMTC 2023 (QII-50)

The number obtained by interchanging the two digits of two digit number is less than the original number by 27. If the difference between the two digits of the number is 3, what is the original number?

Guide / Hint

Hint 1: Let the original number be and the interchanged be .

Hint 2: Set up the equation: , which simplifies to .

Hint 3: Select a valid two-digit number satisfying this condition (e.g., 96).

Solution

Step 1 (Formulate Algebraic Number): Let the original two-digit number be represented by , where is the tens digit and is the units digit ( and ). The number with interchanged digits is .

Step 2 (Set up Equations): We are given:

  1. The interchanged number is less than the original by 27:

  1. The difference between the two digits is 3:

Since the original number is larger than the interchanged one, we must have , so . This is identical to Equation 1.

Step 3 (Identify Solutions): Since the two equations are identical, any two-digit number with tens digit 3 more than its units digit works. The candidates are:

  • (since , interchanged is 69, )

Step 4 (Conclusion): A standard representative correct answer is 96.

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