Find the sum of the first (72) natural numbers.
Answer and explanation
Correct answer: 2628
The sum of the first \(n\) natural numbers is \(S_n=\frac{n(n+1)}{2}\). Hence, \(S_{72}=\frac{72\times73}{2}=36\times73=2628\). Therefore, 2628 is correct. A value such as 2618 can result from an arithmetic error in multiplication or addition. Exam tip: when \(n\) is even, divide \(n\) by 2 first to simplify the calculation.
Frequently asked questions
What is the correct answer to this question?
2628
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(S_n=\frac{n(n+1)}{2}\). Hence, \(S_{72}=\frac{72\times73}{2}=36\times73=2628\). Therefore, 2628 is correct. A value such as 2618 can result from an arithmetic error in multiplication or addition. Exam tip: when \(n\) is even, divide \(n\) by 2 first to simplify the calculation.
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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