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Let w be the width of the rectangle.
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Then the length of the rectangle is 5w units, according to the condition.
Therefore, the perimeter of the rectangle is
w + 5w + w + 5w = 12w.
It is equal to 84 units:
12*w = 84.
Hence, w = = 7 units.
Thus we found that the width of the rectangle is 7 units.
Hence, the length of the rectangle is 5*7 = 35 units.
It means that the area of the rectangle is 7*35 = 245 units.