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12 small squares are divided into : 12 : 3 = 4 (columns)
The length of the edge of each small square is : 12 : 4 = 3 (cm)
The width of the rectangle is : 3 x 3 = 9 (cm)
The length of the rectangle is : 3 x 4 = 12 (cm)
The perimeter of the rectangle is : (9 + 12) x 2 = 42 (cm)
Answer : 42 cm
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The side of a small square is: \(12:4=3\left(cm\right)\)
A line has: \(12:3=4\left(square\right)\)
So the perimeter of the big rectangle is: \(\left(3.4\right).2+\left(3.3\right).2=42\left(cm\right)\)
So the answer is: D
