Which is the sum of the first (70) natural numbers?
Answer and explanation
Correct answer: 2485
The sum of the first \(n\) natural numbers is \(S_n=\frac{n(n+1)}{2}\). Therefore, \(S_{70}=\frac{70\times71}{2}=35\times71=2485\). Hence, option C is correct. \(2475\) may result from an arithmetic error while multiplying or dividing. 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?
2485
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(S_n=\frac{n(n+1)}{2}\). Therefore, \(S_{70}=\frac{70\times71}{2}=35\times71=2485\). Hence, option C is correct. \(2475\) may result from an arithmetic error while multiplying or dividing. 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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