Quadrilateral Query

Geometry Level 3

Consider quadrilateral ABCD whose diagonals are perpendicular and meet at point E.

Minimize the perimeter of ABCD where AB, BC, CD, DA, EA, EB, EC, ED are all different integers.


The answer is 176.

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1 solution

Jeremy Galvagni
Mar 25, 2018

AB=25 BC=39 CD=60 DA=52 EA=20 EB=15 EC=36 ED=48 The perimeter is 176.

Here is a more accurate picture. The yellow and blue are 3-4-5 right triangles scaled by 5 and 12 respectively.

The green and red are 5-12-13 right triangles scaled by 3 and 4 repectively.

So the next smallest size would use 3-4-5 and 8-15-17 triangles, scaled by 8 and 15 and scaled by 3 and 4, so that the diagonal parts are 24, 32, 60, 45, with perimeters 40, 68, 75, 51, for a perimeter length of 234.

Michael Mendrin - 3 years, 1 month ago

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