A rhombus has sides of the same length, which is 100/4=25cm. The diagonals bisect one another at right angles, so the semi-diagonal is 48/2=24cm. The diagonals split the rhombus into 4 right-angled triangles with hypotenuse=25cm and one side=24cm. The length of the third side is √(25^2-24^2)=√49=7. This is the height of each triangle with base 24cm. The area of the rhombus is (4/2)(24)(7)=336sq cm.