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Subjects
Class 9MathematicsSequences and ProgressionsSum of first n natural numbersExpertLevel 61

What is the sum of natural numbers from (90) to (150)?

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Answer and explanation

Correct answer: 7320

There are \(150-90+1=61\) terms from 90 to 150. Using the sum of an arithmetic progression, \(\frac{61}{2}(90+150)=\frac{61}{2}\times240=7320\). Hence, option B is correct. Taking only \(150-90=60\) would miss one endpoint. Exam tip: add \(+1\) when both endpoints are included in the range.

Tags

arithmetic progressionnatural numberssum of termsrange sumsequences and progressions

Frequently asked questions

What is the correct answer to this question?

7320

Why is this the correct answer?

There are \(150-90+1=61\) terms from 90 to 150. Using the sum of an arithmetic progression, \(\frac{61}{2}(90+150)=\frac{61}{2}\times240=7320\). Hence, option B is correct. Taking only \(150-90=60\) would miss one endpoint. Exam tip: add \(+1\) when both endpoints are included in the range.

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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