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Geometry and Trigonometry Difficulty: Hard

Rectangles ABCD and EFGH are similar. The length of each side of EFGH is 6 times the length of the corresponding side of ABCD. The area of ABCD is 54 square units. What is the area, in square units, of EFGH?

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Explanation

Choice D is correct. The area of a rectangle is given by b h , where b is the length of the base of the rectangle and h is its height. Let x represent the length, in units, of the base of rectangle ABCD, and let y represent its height, in units. Substituting x for b and y for h in the formula b h yields x y . Therefore, the area, in square units, of ABCD can be represented by the expression x y . It’s given that the length of each side of EFGH is 6 times the length of the corresponding side of ABCD. Therefore, the length, in units, of the base of EFGH can be represented by the expression 6 x , and its height, in units, can be represented by the expression 6 y . Substituting 6 x for b and 6 y for h in the formula b h yields 6x6y, which is equivalent to 36 x y . Therefore, the area, in square units, of EFGH can be represented by the expression 36 x y . It’s given that the area of ABCD is 54 square units. Since x y represents the area, in square units, of ABCD, substituting 54 for x y in the expression 36 x y yields 3654, or 1,944 . Therefore, the area, in square units, of EFGH is 1,944 .

Choice A is incorrect. This is the area of a rectangle where the length of each side of the rectangle is 16, not 6 , times the length of the corresponding side of ABCD.

Choice B is incorrect. This is the area of a rectangle where the length of each side of the rectangle is 23, not 6 , times the length of the corresponding side of ABCD.

Choice C is incorrect. This is the area of a rectangle where the length of each side of the rectangle is 6, not 6 , times the length of the corresponding side of ABCD.