If (S_n=666), what will be the value of (S_{n+2})?
Answer and explanation
Correct answer: 741
Here, \(S_n\) denotes the sum of the first \(n\) natural numbers. From \(\frac{n(n+1)}{2}=666\), we get \(n=36\). Therefore, \(S_{n+2}=S_{38}=S_{36}+37+38=666+75=741\). Option 740 is one less and does not include the correct sum of the next two natural numbers. Exam tip: to find \(S_{n+2}\), add \(n+1\) and \(n+2\) to \(S_n\).
Frequently asked questions
What is the correct answer to this question?
741
Why is this the correct answer?
Here, \(S_n\) denotes the sum of the first \(n\) natural numbers. From \(\frac{n(n+1)}{2}=666\), we get \(n=36\). Therefore, \(S_{n+2}=S_{38}=S_{36}+37+38=666+75=741\). Option 740 is one less and does not include the correct sum of the next two natural numbers. Exam tip: to find \(S_{n+2}\), add \(n+1\) and \(n+2\) to \(S_n\).
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.
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