An isosceles triangular piece is cut from a square plate of side l. The piece is one-fourth of the square and mass of the remaining plate is M. The moment of inertia of the plate about an axis passing through O and perpendicular to its plane is

Mass of each of the four parts =M3Mass of the plate including the cut piece =4M3 Moment of inertia of the whole plate (including the cut piece) about the said axis =4M3l26Now moment of inertia of the remaining portion should be 3/4 of the above = Ml26.