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Number theory Difficulty 3.8 AMC 10/12 Find the answer United States

A rectangle has integer length sides and an area of 20242024. What is the least possible perimeter of the rectangle?

Pick one

Solution

Note that 2024=44462024 = 44 \cdot 46. A 44×4644 \times 46 rectangle will have perimeter 2(44+46)=1802(44 + 46) = 180. It is straightforward to check the other possible dimensions to show that this gives the rectangle with the least possible perimeter:
* 23×8823 \times 88 gives a perimeter of 2(23+88)=2222(23 + 88) = 222.
* 22×9222 \times 92 gives a perimeter of 2(22+92)=2282(22 + 92) = 228.
* 11×18411 \times 184 gives a perimeter of 2(11+184)=3902(11 + 184) = 390.
* If one of the dimensions is 11, 22, 44, or 88, then the other dimension is greater than 200200, yielding rectangles with greater perimeters.
Thus the least possible perimeter is 180180.

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Source: MathNet, licensed CC-BY-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.