How much is the sum of the first (40) natural numbers?
Answer and explanation
Correct answer: 820
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=40\), we get \(\frac{40\times41}{2}=20\times41=820\). Therefore, 820 is the correct answer. A value such as 800 may result from \(40\times20\), but that is not the correct sum formula. Exam tip: for the sum of consecutive natural numbers from 1 to \(n\), use \(\frac{n(n+1)}{2}\).
Frequently asked questions
What is the correct answer to this question?
820
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=40\), we get \(\frac{40\times41}{2}=20\times41=820\). Therefore, 820 is the correct answer. A value such as 800 may result from \(40\times20\), but that is not the correct sum formula. Exam tip: for the sum of consecutive natural numbers from 1 to \(n\), use \(\frac{n(n+1)}{2}\).
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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