Answer:
Number of trees in both sides = 16
Step-by-step explanation:
The first tree will be at 20 feet from there trees will be 50 feet apart.
These are in arithmetic progression
20, 70, 120 .............................
Last tree will at 370 feet.
We have
a + ( n- 1 ) d = 370
a = 20 and d = 50
20 + ( n- 1 ) x 50 = 370
( n- 1 ) x 50 = 350
( n- 1 ) = 7
n = 8 trees
Number of trees in one side = 8
Number of trees in both sides = 16