After Will had stacked up 12 chairs in the canteen after a party, he noticed 3 things. Firstly, each of the chairs was stacked the same height above the other. Secondly, the foot of the fourth chair was 19.2 cm above that of the first. Thirdly, the chairs reached a height of 154.9 cm. What is the height of each chair?
Number of chairs that contributed to the height of 19.2 cm above the first chair
= 4 - 1
= 3

Height increase with each additional stacked chair
= 19.2 ÷ 3
= 6.4 cm

Number of chairs stacked on top of the first chair
= 12 - 1
= 11

Height increase of 11 additional stacked chairs
= 11 x 6.4
= 70.4 cm

Height of one chair
= 154.9 - 70.4
= 84.5 cm

Answer(s): 84.5 cm