To solve the application problem of tree planting in primary school mathematics, we must master the basic quantitative relationship of such problems (plant spacing × number of plants = total length; Total length/plant spacing = number of trees; Total length, number of plants = plant spacing). According to the meaning of the question, choose the corresponding quantitative relationship correctly and answer according to the relationship.

2.

There are several situations about planting trees, and the solutions are slightly different. Check carefully when you answer questions.

(1) Plant trees around (the playground, etc.). ) and directly apply the basic relational expression.

② Plant trees along a straight line (one side of the road), because one tree will be planted at both ends, so "total length ÷ plant spacing+1 = number of plants".

(3) Plant trees along a straight line (on both sides of the road), and the number of trees should be ×2.