What is obtained by subtracting the sum of the first (125) natural numbers from the sum of the first (150) natural numbers?
Answer and explanation
Correct answer: 3450
The sum of the first 150 natural numbers is \(\frac{150\times151}{2}=11325\), and the sum of the first 125 natural numbers is \(\frac{125\times126}{2}=7875\). Therefore, the difference is \(11325-7875=3450\). It is also the sum of the numbers from 126 to 150. Although 3425 is close, it does not result from the correct calculation. Exam tip: interpret such a difference as the sum of the remaining consecutive terms.
Frequently asked questions
What is the correct answer to this question?
3450
Why is this the correct answer?
The sum of the first 150 natural numbers is \(\frac{150\times151}{2}=11325\), and the sum of the first 125 natural numbers is \(\frac{125\times126}{2}=7875\). Therefore, the difference is \(11325-7875=3450\). It is also the sum of the numbers from 126 to 150. Although 3425 is close, it does not result from the correct calculation. Exam tip: interpret such a difference as the sum of the remaining consecutive terms.
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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