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Difficulty: 3/102023 IOQM 2023 (Q3)

Let and be positive integers such that:

Find the smallest possible value of .

Guide / Hint

Hint 1: Take the reciprocals of the fractions in the inequality, which reverses the signs: .

Hint 2: Rewrite the bounds as mixed numbers to isolate the fractional part: .

Hint 3: Let and find the bounds for in terms of . Test small integer values of starting from 1 to find the minimum integer .

Solution

Step 1: Take the reciprocals of the inequality:

Step 2: Write these fractions as mixed numbers:

Step 3: Subtract 2 from all parts of the inequality:

Step 4: Let . Since and are integers, must also be an integer:

Step 5: We test small positive integers for to find one that allows an integer value for :

  • If : no integer solution.

  • If : no integer solution.

  • If : .

Step 6: For and , we solve for :

Thus, the smallest possible value of is .

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    2023 IOQM 2023 Q3 - Olympiad Math Olympiad Question | Leminno