The average height of a starfruit tree, a persimmon tree and a mangosteen tree is 8.8 m. The mangosteen tree is four times as tall as the persimmon tree and 0.6 m taller than the starfruit tree. Find the average height of the starfruit tree and the persimmon tree.
Total height of the starfruit tree, the persimmon tree and the mangosteen tree
= 3 x 8.8
= 26.4 m

Height of the persimmon tree = 1 u
Height of the mangosteen tree = 4 u
Height of the starfruit tree = 4 u - 0.6

Total height of the starfruit tree, the persimmon tree and the mangosteen tree
= 1 u + 4 u + 4 u - 0.6
= 9 u - 0.6

9 u - 0.6 = 26.4
9 u = 26.4 + 0.6
9 u = 27

1 u = 27 ÷ 9 = 3

Total height of the starfruit tree and the persimmon tree
= 1 u + 4 u - 0.6
= 5 u - 0.6
= 5 x 3 - 0.6
= 15 - 0.6
= 14.4 m

Average height of the starfruit tree and the persimmon tree
= 14.4 ÷ 2
= 7.2 m

Answer(s): 7.2 m