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Class 9MathematicsSequences and ProgressionsSum of first n natural numbersEasyLevel 63
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If the sum of the first (n) natural numbers is (45), what is (n)?

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Answer and explanation

Correct answer: (9)

(S_9=\frac{9\times10}{2}=45), so (n=9). In such questions, checking options in the formula is fast.

Related tags

MathSequencesNatural-NumbersSum

Frequently asked questions

What is the correct answer to this question?

(9)

Why is this the correct answer?

(S_9=\frac{9\times10}{2}=45), so (n=9). In such questions, checking options in the formula is fast.

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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  4. 4If a = 7 and d = 3, what is the sum of the first 6 terms?
  5. 5What is the sum of the first 6 terms of the arithmetic progression (15, 21, 27, 33, ...)?
  6. 6What is the sum of the first (10) natural numbers?
  7. 7Find the sum of the first (20) natural numbers.
  8. 8If \(S_n=\frac{n(n+1)}{2}\), what is \(S_{15}\)?
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  10. 10Which is the sum of the first (30) natural numbers?
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