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Class 9 Mathematics Sequences and Progressions Sum of first n natural numbersExpertLevel 59

If (S_n=11781), what is the value of (n)?

Answer and explanation

Correct answer: (153)

(S_{153}=\frac{153\times154}{2}=11781), so (n=153). For large values, using (2S_n) makes identification easier.

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mathsequencesnatural-numberssum

Frequently asked questions

What is the correct answer to this question?

(153)

Why is this the correct answer?

(S_{153}=\frac{153\times154}{2}=11781), so (n=153). For large values, using (2S_n) makes identification easier.

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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