If the difference between an interior angle of a regular polygon of (n + 1) sides and an interior angle of a regular polygon of n sides is 4°; find the value of n.

Also, state the difference between their exterior angles.

In a quadrilateral ABCD; angles A, B, C and D are in the ratio 3 : 2 : 1 : 4. Prove that AD is parallel to BC.

In the diagram below; P and Q are midpoints of sides BC and AD respectively of the parallelogram ABCD. If side AB = diagonal BD; prove that the quadrilateral BPDQ is a rectangle.

ABCD is a parallelogram. If AB = 2AD and P is the mid-point of CD; prove that : ∠APB = 90°.