The sum of the first (9) natural numbers is equal to which value?
Answer and explanation
Correct answer: 45
The first 9 natural numbers are \(1,2,3,\ldots,9\). The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=9\) gives \(\frac{9\times10}{2}=45\). The close distractor 36 is the sum of the first 8 natural numbers. Exam tip: remember that the formula uses both \(n\) and \(n+1\).
Frequently asked questions
What is the correct answer to this question?
45
Why is this the correct answer?
The first 9 natural numbers are \(1,2,3,\ldots,9\). The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=9\) gives \(\frac{9\times10}{2}=45\). The close distractor 36 is the sum of the first 8 natural numbers. Exam tip: remember that the formula uses both \(n\) and \(n+1\).
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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