What is obtained by adding (46), (47), and (48) to the sum of the first (45) natural numbers?
Answer and explanation
Correct answer: \(S_{48}\)
If \(S_{45}=1+2+\cdots+45\), then adding \(46\), \(47\), and \(48\) gives \(1+2+\cdots+45+46+47+48=S_{48}\). \(S_{47}\) would include terms only up to 47; adding 48 makes the result \(S_{48}\). Exam tip: when consecutive next natural numbers are added, the subscript of the sum becomes the last number added.
Frequently asked questions
What is the correct answer to this question?
\(S_{48}\)
Why is this the correct answer?
If \(S_{45}=1+2+\cdots+45\), then adding \(46\), \(47\), and \(48\) gives \(1+2+\cdots+45+46+47+48=S_{48}\). \(S_{47}\) would include terms only up to 47; adding 48 makes the result \(S_{48}\). Exam tip: when consecutive next natural numbers are added, the subscript of the sum becomes the last number added.
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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