NCERT Class XI Mathematics - Sequences and Series - Solutions
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Question : 15
Total: 106
Find the sum of odd integers from 1 to 2001.
Solution:
We have to find 1 + 3 + 5 + ......... + 2001
This is an A.P. with first term a = 1, common difference d = 3 – 1 = 2 and last term l = 2001
∴ l = a + (n – 1)d ⇒ 2001 = 1 + (n – 1)2
⇒ 2001 = 1 + 2n – 2 ⇒ 2n = 2001 + 1
⇒ n = 1001
⇒ Sum =
This is an A.P. with first term a = 1, common difference d = 3 – 1 = 2 and last term l = 2001
∴ l = a + (n – 1)d ⇒ 2001 = 1 + (n – 1)2
⇒ 2001 = 1 + 2n – 2 ⇒ 2n = 2001 + 1
⇒ n = 1001
⇒ Sum =
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