The average height of a mangosteen tree, a mango tree and a durian tree is 4.4 m. The durian tree is thrice as tall as the mango tree and 0.8 m taller than the mangosteen tree. Find the average height of the mangosteen tree and the mango tree.
Total height of the mangosteen tree, the mango tree and the durian tree
= 3 x 4.4
= 13.2 m

Height of the mango tree = 1 u
Height of the durian tree = 3 u
Height of the mangosteen tree = 3 u - 0.8

Total height of the mangosteen tree, the mango tree and the durian tree
= 1 u + 3 u + 3 u - 0.8
= 7 u - 0.8

7 u - 0.8 = 13.2
7 u = 13.2 + 0.8
7 u = 14

1 u = 14 ÷ 7 = 2

Total height of the mangosteen tree and the mango tree
= 1 u + 3 u - 0.8
= 4 u - 0.8
= 4 x 2 - 0.8
= 8 - 0.8
= 7.2 m

Average height of the mangosteen tree and the mango tree
= 7.2 ÷ 2
= 3.6 m

Answer(s): 3.6 m