In a school, students thought of planting trees in and around the school to reduce airpollution. It was decided that the number of trees, that each section of each class willplant, will be the same as the class, in which they are studying, e.g., a section of Class Iwill plant 1 tree, a section of Class II will plant 2 trees and so on till Class XII. There arethree sections of each class. How many trees will be planted by the students?
Since each section of class 1 will plant 1 tree, so 3 trees will be planted by 3 sections of class 1.
Similarly,
No. of trees planted by 3 sections of class 2 = 6
No. of trees planted by 3 sections of class 3 = 9
No. of trees planted by 3 sections of class 4 = 12
We have; a = 3, d = 3 and n = 12
We can find the total number of trees as follows:
= 6(6 + 33)
= 6*39
= 234