Advertisements
Advertisements
प्रश्न
In a school, students decided to plant trees in and 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 double of the class in which they are studying. If there are 1 to 12 classes in the school and each class has two sections, find how many trees were planted by the students.
Advertisements
उत्तर
Let a be the first term and d be the common difference.
We know that, sum of first n terms = Sn = \[\frac{n}{2}\][2a + (n − 1)d]
It can be observed that the number of trees planted by the students forms an A.P.
2, 4, 6, 8, ... , 24
Here, a = 2, d = 2 and n = 12.
= 6(26)
= 156
Therefore, trees planted by 1 section of all the classes = 156.
Number of trees planted by 2 sections of all the classes = 2 × 156 = 312
Thus, 312 trees were planted by the students.
APPEARS IN
संबंधित प्रश्न
Find the sum of first 30 terms of an A.P. whose second term is 2 and seventh term is 22
In a school, students thought of planting trees in and 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?
Which term of the progression 20, 19`1/4`,18`1/2`,17`3/4`, ... is the first negative term?
If the ratio of the sum of the first n terms of two A.Ps is (7n + 1) : (4n + 27), then find the ratio of their 9th terms.
In a flower bed, there are 43 rose plants in the first row, 41 in second, 39 in the third, and so on. There are 11 rose plants in the last row. How many rows are there in the flower bed?
If the sum of first n terms is (3n2 + 5n), find its common difference.
How many terms of the AP 63, 60, 57, 54, ….. must be taken so that their sum is 693? Explain the double answer.
Find four consecutive terms in an A.P. whose sum is 12 and sum of 3rd and 4th term is 14.
(Assume the four consecutive terms in A.P. are a – d, a, a + d, a +2d)
If the sum of first p terms of an A.P. is equal to the sum of first q terms then show that the sum of its first (p + q) terms is zero. (p ≠ q)
The sum of first seven terms of an A.P. is 182. If its 4th and the 17th terms are in the ratio 1 : 5, find the A.P.
Write the common difference of an A.P. whose nth term is an = 3n + 7.
For what value of p are 2p + 1, 13, 5p − 3 are three consecutive terms of an A.P.?
If the first, second and last term of an A.P. are a, b and 2a respectively, its sum is
The common difference of the A.P. is \[\frac{1}{2q}, \frac{1 - 2q}{2q}, \frac{1 - 4q}{2q}, . . .\] is
Q.19
If the second term and the fourth term of an A.P. are 12 and 20 respectively, then find the sum of first 25 terms:
Obtain the sum of the first 56 terms of an A.P. whose 18th and 39th terms are 52 and 148 respectively.
The sum of first n terms of the series a, 3a, 5a, …….. is ______.
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is ______.
The sum of 40 terms of the A.P. 7 + 10 + 13 + 16 + .......... is ______.
