Question 1 :
Find the sum of the first 15 terms in $a_n = 9 – 5n$

Question 2 :
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?

Question 3 :
Find the sum of the first 15 terms in $a_n = 3 + 4n$.

Question 4 :
How many terms of the AP : 9, 17, 25, . . . must be taken to give a sum of 636?

Question 5 :
The 17th term of an AP exceeds its 10th term by 7. Find the common difference.

Question 6 :
In an AP, given $a_n = 4, d = 2, S_n = –14$, find n and a.

Question 7 :
In an AP, given $a = 2, d = 8, S_n = 90$, find n and $a_n$.

Question 8 :
If the sum of the first n terms of an AP is $4n – n^2$, What is the 3rd term ?

Question 9 :
Determine the AP whose third term is 16 and the 7th term exceeds the 5th term by 12.

Question 10 :
The first and the last terms of an AP are 17 and 350 respectively. If the common difference is 9, how many terms are there in the AP?

Question 11 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b19bc8273b230584979a15.JPG' /> In the above fig. In a potato race, a bucket is placed at the starting point, which is 5 m from the first potato, and the other potatoes are placed 3 m apart in a straight line. There are ten potatoes in the line. A competitor starts from the bucket, picks up the nearest potato, runs back with it, drops it in the bucket, runs back to pick up the next potato, runs to the bucket to drop it in, and she continues in the same way until all the potatoes are in the bucket. What is the total distance the competitor has to run?

Question 12 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b19bc6273b230584979a13.JPG' /> In the above fig. A spiral is made up of successive semicircles, with centres alternately at A and B, starting with centre at A, of radii 0.5 cm, 1.0 cm, 1.5 cm, 2.0 cm, . . . as shown in above figure. What is the total length of such a spiral made up of thirteen consecutive semicircles?

Question 13 :
Find the sum of the following AP: 0.6, 1.7, 2.8, . . ., to 100 terms.

Question 14 :
In an AP, given l = 28, S = 144, and there are total 9 terms. Find a.

Question 15 :
The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.

Question 16 :
In an AP, given $a_{12} = 37, d = 3$, find a and $S_{12}$.

Question 17 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b19bc4273b230584979a10.JPG' /> In the above fig, find the missing value corresponding to (i)

Question 19 :
A contract on construction job specifies a penalty for delay of completion beyond a certain date as follows: Rs 200 for the first day, Rs 250 for the second day, Rs 300 for the third day, etc., the penalty for each succeeding day being Rs 50 more than for the preceding day. How much money the contractor has to pay as penalty, if he has delayed the work by 30 days?

Question 20 :
An AP consists of 50 terms of which 3rd term is 12 and the last term is 106. Find the 29th term.