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
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CBSE Class 10 Sample Paper for 2019 Boards
Last updated at Aug. 28, 2020 by Teachoo
Question 4
If n ^{ th } term of an A.P. is (2n + 1), what is the sum of its first three terms?
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