When is the sum of the first n natural numbers odd?
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Answer and explanation
Correct answer: जब n को 4 से विभाजित करने पर शेषफल 1 या 2 हो
The sum is \(S_n=\frac{n(n+1)}{2}\). It is odd only when n leaves remainder 1 or 2 on division by 4. Merely knowing that n is odd or even is not enough. Exam tip: check \(n\bmod 4\).
Frequently asked questions
What is the correct answer to this question?
जब n को 4 से विभाजित करने पर शेषफल 1 या 2 हो
Why is this the correct answer?
The sum is \(S_n=\frac{n(n+1)}{2}\). It is odd only when n leaves remainder 1 or 2 on division by 4. Merely knowing that n is odd or even is not enough. Exam tip: check \(n\bmod 4\).
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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