All stands on same base, means all have same radii.
Height of hemisphere, h = radius = r
Height of cone = height of cylinder = h =r
now. volume of cone = (1/3)πr²h
volume of hemisphere= (2/3)πr³ = [∵r=h ]
volume of cylinder= πr²h = (3/3)πr²h
cone:hemisphere:cylinder = [(1/3)πr²h]:[(2/3)πr²h]:[(3/3)πr²h]