The GMAT Math practice question is a problem on polygons and their shapes in geometry
Vertices of a quadrilateral ABCD are A(0, 0), B(4, 5), C(9, 9) and D(5, 4). What is the shape of the quadrilateral?
- Square
- Rectangle but not a square
- Rhombus
- Parallelogram but not a rhombus
- Kite
The correct choice is (C) and the correct answer is
Rhombus.
The lengths of the four sides, AB, BC, CD and DA are all equal to

.
Hence, the given quadrilateral is either a Rhombus or a Square.
Now let us compute the lengths of the two diagonals AC and BD.
The length of AC is

and the length of BD is

.
As the diagonals are not equal and the sides are equal, the given quadrilateral is a Rhombus.
Properties of a square
A. All 4 sides are equal
B. Opposite angles are equal and supplementary
C. Diagonals are equal and bisect each other at right angles
Properties of a Rhombus
A. All 4 sides are equal
B. Opposite angles are equal but not supplementary
C. Diagonals are not equal but bisect each other at right angles.