What remains after subtracting (1500) from the sum of the first (65) natural numbers?
Answer and explanation
Correct answer: 645
The sum of the first 65 natural numbers is \(\frac{65\times66}{2}=2145\). Therefore, the required value is \(2145-1500=645\), so option D is correct. A nearby value such as 640 is incorrect because no extra rounding is done after finding the sum and subtracting. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of the first \(n\) natural numbers.
Frequently asked questions
What is the correct answer to this question?
645
Why is this the correct answer?
The sum of the first 65 natural numbers is \(\frac{65\times66}{2}=2145\). Therefore, the required value is \(2145-1500=645\), so option D is correct. A nearby value such as 640 is incorrect because no extra rounding is done after finding the sum and subtracting. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of the first \(n\) natural numbers.
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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