Answer: The answer is six.
Step-by-step explanation: There are six important properties of a parallelogram. Please see the attached figure. The properties are as follows :
(i) The opposite sides of a parallelogram are parallel and congruent, i.e., PQ║RS, QR║PS, PQ ≅ RS and QR ≅ PS.
(ii) The opposite angles of a parallelogram are congruent, i.e., ∠P = ∠R and ∠Q = ∠S.
(iii) The diagonals of a parallelogram bisect each other, i.e., OP = OR and OQ = OS.
(iv) Consecutive angles of a parallelogram are supplementary. For example, ∠P + ∠Q = 180°.
(v) If one angles of a parallelogram is 90°, then all the angles are 90°.
(vi) Each diagonal of a parallelogram separates it into two congruent triangles. For example, ΔPQR ≅ ΔSQR.
