Understanding Q...

ABCD is a parallelogram in which $$\angle DAC = 40^{\circ} ; \angle BAC = 30^{\circ}; \angle DOC = 105^{\circ}$$ ; then $$\angle CDO$$ equals :

If PQRS is a parallelogram, then $$\angle{Q}- \angle{S}$$ is equal to :

The diagonals of a parallelogram PQRS intersect at O. If $$ \angle QOR= 90^{\circ}\ and\ \angle QSR=50^{\circ}, \ then\  \angle ORS$$ is :

In the given figure, ABCD is a parallelogram. If $$\angle B = 100^{\circ}$$, then ($$\angle A + \angle C$$) is equal to :

Consider the following statements:
(1) The diagonals of a parallelogram are equal.
(2) The diagonals of a square are perpendicular     
       to each other.
(3) If the diagonals of a quadrilateral intersect at   
       right angles, it is not necessarily a rhombus.
(4) Every quadrilateral is either a trapezium or a 
       parallelogram or a kite.
Which of the above statements is/are correct?

Two adjacent angles of a parallelogram are $$(2x + 30)^{\circ}$$ and $$(3x + 30)^{\circ}$$. The value of $$x$$ is :

If the sum of all interior angles  of a convex polygon is $$1440^{\circ}$$, then the number of sides of the polygon is?

The measurement of each angle of a polygon is 160$$^{\circ}$$. The number of its sides is?

The sum of the measures of all the angles of a pentagon are :

Each interior angle of a regular polygon is $$144^0$$. Find the interior angle of a regular polygon which has double the number of sides as the first polygon.