Let x = 2, y = 3 and z = 4 where x < y < z volume 2 × 3 × 4 = 24 cm3 Case I when x is increased by 1 3 × 3 × 4 = 36 cm3 Case II when y is increased by 1 2 × 4 × 4 = 32 cm3 Case III when z is increased by 1 2 × 3 × 5 = 30 cm3 Volume is greatest when x is increased.