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Algebra Difficulty 2.0 Junior Find the answer

A rectangle has positive integer side lengths and an area of 24. What perimeter of the rectangle cannot be?

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

Since the rectangle has positive integer side lengths and an area of 24, its length and width must be a positive divisor pair of 24. Therefore, the length and width must be 24 and 1, or 12 and 2, or 8 and 3, or 6 and 4. Since the perimeter of a rectangle equals 2 times the sum of the length and width, the possible perimeters are 2(24+1)=502(24+1)=50, 2(12+2)=282(12+2)=28, 2(8+3)=222(8+3)=22, 2(6+4)=202(6+4)=20. These all appear as choices, which means that the perimeter of the rectangle cannot be 36.

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