What is obtained by adding (30) and (31) to the sum of the first (29) natural numbers?
Answer and explanation
Correct answer: \(S_{31}\)
If \(S_n\) denotes the sum of the first \(n\) natural numbers, then adding the next two numbers to \(S_{29}\) gives \(S_{29}+30+31=S_{31}\). \(S_{30}\) includes only up to 30, so it is not correct. Exam tip: when consecutive next terms are added to a partial sum, increase the subscript accordingly.
Frequently asked questions
What is the correct answer to this question?
\(S_{31}\)
Why is this the correct answer?
If \(S_n\) denotes the sum of the first \(n\) natural numbers, then adding the next two numbers to \(S_{29}\) gives \(S_{29}+30+31=S_{31}\). \(S_{30}\) includes only up to 30, so it is not correct. Exam tip: when consecutive next terms are added to a partial sum, increase the subscript accordingly.
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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