1) How many trees can be placed at most on both sides of a wide avenue that is 180 meters long, placed 15 meters apart from each other?
(A) 20
(B) 22
(C) 24
(D) 26
(E) 28.
1) The answer is (D)

On each side, there can be a maximum of 13 trees: one at the beginning and 12 more spaced $15 \mathrm{~m}$ apart from each other. The last one will thus be exactly at the end of the avenue.