9. To plant willow trees and peach trees along the edges of a rectangular school playground, it is known that the playground is 150 meters long and 60 meters wide. It is required that the distance between every two willow trees is 10 meters, and the distance between every two peach trees is also 10 meters. Additionally, each willow tree must have peach trees on both sides, and each peach tree must have willow trees on both sides. How many willow trees and how many peach trees are needed?
【Solution】Solution:
Perimeter: $(150+60) \times 2=420$ (meters)
$$
10 \div 2=5 \text { (meters) }
$$

Total number of trees: $420 \div 5=84$ (trees)
Peach trees, Willow trees $84 \div 2=42$ (trees)
Answer: A total of 42 peach trees and 42 willow trees are needed.