In a school, students thought of planting trees in an around the school to reduce air pollution. It was decided that the number of trees, that each section of each class will plant, will be the same as the class in which they are studying, e.g., a section of class - I will plant 1 tree, a section of class II will plant 2 trees and so on till class XII. There are three sections of each class. How many trees will be planted by the students? What value can you infer from the planting the trees?

### Asked by Topperlearning User | 25th Sep, 2017, 10:14: AM

There are three sections of each class and it is given that the number of trees planted by any class is equal to class number.

The number of trees planted by class I = number of sections _{}1 = 3 _{}1 = 3

The number of trees planted by class II = number of sections _{}2 = 3 _{}2 = 6

The number of trees planted by class III = number of sections _{}3 = 3 _{}3 = 9

Therefore, we have the sequence: 3, 6, 9, ...., (12 terms)

To find total number of trees planted by all the students, we need to find sum of the 12 terms of the sequence.

First term = a = 3

Common difference = d = 6 - 3 = 3

n = 12

S_{n}= [2a+(n-1)d]

S_{12 }= _{}[6+(12 - 1)(3)] = 6(6+33) = 6 _{}39 = 234

Thus, in total 234 trees will be planted by the students.

Values inferred are environmental friendly and social.

### Answered by | 25th Sep, 2017, 12:14: PM

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