How much is the sum of the first (85) natural numbers?
Answer and explanation
Correct answer: 3655
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=85\), we get \(\frac{85\times86}{2}=85\times43=3655\). Therefore, option C is correct. A value such as \(3645\) results from an arithmetic error in the calculation. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of consecutive natural numbers starting from 1.
Frequently asked questions
What is the correct answer to this question?
3655
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=85\), we get \(\frac{85\times86}{2}=85\times43=3655\). Therefore, option C is correct. A value such as \(3645\) results from an arithmetic error in the calculation. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of consecutive natural numbers starting from 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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