Question 4
If n th term of an A.P. is (2n + 1), what is the sum of its first three terms?

CBSE Class 10 Sample Paper for 2019 Boards
CBSE Class 10 Sample Paper for 2019 Boards
Last updated at Dec. 16, 2024 by Teachoo
Question 4
If n th term of an A.P. is (2n + 1), what is the sum of its first three terms?
Transcript
Question 4 If nth term of an A.P. is (2n + 1), what is the sum of its first three terms? Given an = 2n + 1 We need to find sum of first three terms Finding first three terms a1 = 2(1) + 1 = 2 + 1 = 3 a2 = 2(2) + 1 = 4 + 1 = 5 a3 = 2(3) + 1 = 6 + 1 = 7 1/2 marks for finding a1, a2, a3 So, Sum of first three terms = a1 + a2 + a3 = 3 + 5 + 7 = 15