After Ian had stacked up 13 chairs in the hall 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 ninth chair was 55.2 cm above that of the first. Thirdly, the chairs reached a height of 158 cm. What is the height of each chair?
Number of chairs that contributed to the height of 55.2 cm above the first chair
= 9 - 1
= 8

Height increase with each additional stacked chair
= 55.2 ÷ 8
= 6.9 cm

Number of chairs stacked on top of the first chair
= 13 - 1
= 12

Height increase of 12 additional stacked chairs
= 12 x 6.9
= 82.8 cm

Height of one chair
= 158 - 82.8
= 75.2 cm

Answer(s): 75.2 cm