If (S_n=1326), what will be the value of (S_{n+7})?
Answer and explanation
Correct answer: 1711
The sum of the first \(n\) natural numbers is \(S_n=\frac{n(n+1)}{2}\). From \(\frac{n(n+1)}{2}=1326\), we get \(n=51\). Hence, \(n+7=58\), and \(S_{58}=\frac{58\times59}{2}=1711\). Option 1671 is not correct because it is not the sum of natural numbers up to 58. Exam tip: first determine \(n\) from the given sum, then apply the formula at the new index.
Frequently asked questions
What is the correct answer to this question?
1711
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(S_n=\frac{n(n+1)}{2}\). From \(\frac{n(n+1)}{2}=1326\), we get \(n=51\). Hence, \(n+7=58\), and \(S_{58}=\frac{58\times59}{2}=1711\). Option 1671 is not correct because it is not the sum of natural numbers up to 58. Exam tip: first determine \(n\) from the given sum, then apply the formula at the new index.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Sum of first n natural numbers.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
