Which sum is obtained by adding (37+38) to the sum of the first (36) natural numbers?
Answer and explanation
Correct answer: \(S_{38}\)
If \(S_n\) denotes the sum of the first \(n\) natural numbers, then \(S_{36}=1+2+\cdots+36\). Adding the next two consecutive terms, 37 and 38, gives \(1+2+\cdots+36+37+38=S_{38}\). \(S_{37}\) includes terms only up to 37, so it is not correct. Exam tip: each next term added to a partial sum increases its subscript by 1.
Frequently asked questions
What is the correct answer to this question?
\(S_{38}\)
Why is this the correct answer?
If \(S_n\) denotes the sum of the first \(n\) natural numbers, then \(S_{36}=1+2+\cdots+36\). Adding the next two consecutive terms, 37 and 38, gives \(1+2+\cdots+36+37+38=S_{38}\). \(S_{37}\) includes terms only up to 37, so it is not correct. Exam tip: each next term added to a partial sum increases its subscript by 1.
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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