CBSE Class 10 Sample Paper for 2018 Boards

Class 10
Solutions of Sample Papers for Class 10 Boards

### The sum of first n terms of an AP is given by S n = 2n 2 + 3n . Find the sixteenth term of the AP.

This is a question of CBSE Sample Paper - Class 10 - 2017/18.

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### Transcript

Question 8 The sum of first n terms of an AP is given by Sn = 2n2 + 3n . Find the sixteenth term of the AP. Given Sn = 2n2 + 3n Taking n = 1 S1 = 2 12 + 3 1 = 2 + 3 = 5 So, Sum of first term of AP is 5 But sum of first term will be the first term So, First term = a = 5 Taking n = 2 in Sn S1 = 2 22 + 3 2 S2 = 2 4 + 6 S2 = 8 + 6 S2 = 14 Sum of first 2 terms is 14 Finding 2nd term Sum of first 2 terms is 14 First term + Second term = 14 5 + a2 = 14 a2 = 14 5 a2 = 9 Hence in AP , First term = a = 3 Common difference = d = Second term First term = 9 5 = 4 We need to find 16th term We know that an = a + (n 1) d a16 = a + (16 1) d = a + 15d = 5 + 15 4 = 5 + 60 = 65

#### Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.