Find the total number of ways in which a black square and a white square can be selected from a chessboard such that both the squares lie either in the same row or in the same column.

P is a point outside the circle with centre O. If a straight line drawn through P intersects the circle at points A and B such that and 90⁰ < ∠AOB < 120⁰, which of the following could be the radius (in cm) of the circle?

In the above triangle ABC, find the co-ordinates of the foot of the perpendicular drawn from B to AC.