Back to Mathematical Olympiad
Difficulty: 5/102024 IOQM 2024 (Q30)

Let ABC be right-angled triangle with ∠B = 90° . Let the length of the altitude BD be equal to 12. What is the minimum possible length of AC, given that AC and the perimeter of triangle ABC are integers?

Guide / Hint

Hint 1: Start by analyzing the initial conditions and setting up the basic equations. Let + = I Iin integer.

Hint 2: Look for algebraic properties, symmetry, or geometric theorems to simplify. a2 + c2 = I2 – 24b = b2.

Hint 3: Proceed with the final algebraic steps to solve the system. I2 = Ix solve for the final valueb.

Solution

Step 1: Let + = I Iin integer

Step 2: a2 + c2 = I2 – 24b = b2

Step 3: I2 = Ix = 12b

Step 4: I 2 − 48b  0

Step 5: b 2 + 24 l  0  24

Step 6: Let = – 12  36

Step 7: I2 = k2 – 144

Step 8: 144 = (k – I) (k + I)

Step 9: For = 37, I = 35

Step 10: I = 25 is minimum value

Step 11: ❑ ❑ ❑

Ready to track your progress and master these topics?

Create a free account