What is the value of (1+2+3+\cdots+19)?
Answer and explanation
Correct answer: 190
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Here, \(n=19\), so \(\frac{19\times20}{2}=19\times10=190\). The values 180, 200, and 210 do not result from this formula. Exam tip: use the last number in the series as \(n\) before applying the formula.
Frequently asked questions
What is the correct answer to this question?
190
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Here, \(n=19\), so \(\frac{19\times20}{2}=19\times10=190\). The values 180, 200, and 210 do not result from this formula. Exam tip: use the last number in the series as \(n\) before applying the formula.
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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