Two cylindrical drums are similar in shape and the larger holds eight times as much as the smaller. The smaller drum is 30 cm tall. Find the height of the larger one in cm.

Capacity grows as the cube of the linear ratio, so a ratio of 8 in volume means ∛8 = 2 in length. Height = $30\times 2=60$ cm. (Multiplying the height by 8 gives 240 cm; by 4, as though volume followed the square, gives 120 cm; by 3 gives 90 cm.)