The average height of a durian tree, a coconut tree and a guava tree is 4.4 m. The guava tree is twice as tall as the coconut tree and 1.8 m taller than the durian tree. Find the average height of the durian tree and the coconut tree.
Total height of the durian tree, the coconut tree and the guava tree
= 3 x 4.4
= 13.2 m

Height of the coconut tree = 1 u
Height of the guava tree = 2 u
Height of the durian tree = 2 u - 1.8

Total height of the durian tree, the coconut tree and the guava tree
= 1 u + 2 u + 2 u - 1.8
= 5 u - 1.8

5 u - 1.8 = 13.2
5 u = 13.2 + 1.8
5 u = 15

1 u = 15 ÷ 5 = 3

Total height of the durian tree and the coconut tree
= 1 u + 2 u - 1.8
= 3 u - 1.8
= 3 x 3 - 1.8
= 9 - 1.8
= 7.2 m

Average height of the durian tree and the coconut tree
= 7.2 ÷ 2
= 3.6 m

Answer(s): 3.6 m