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.

In the figure above, seven congruent rectangles are assembled together perfectly to form a bigger rectangle of perimeter 130 cm. Find the area (in sq.cm) of the bigger rectangle.

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?