Find the sum of all natural numbers from 1 to 25.
Answer and explanation
Correct answer: 325
The numbers from 1 to 25 are the first 25 natural numbers, so the standard sum formula applies: S_n = n(n + 1)/2. Taking n = 25, we get S_25 = 25 × 26 / 2. Since 26 divided by 2 is 13, the product becomes 25 × 13 = 325. Therefore, option B is correct. Pairing the terms also confirms the result: 1 + 25 = 26, 2 + 24 = 26, and so on; there are 12 such pairs, with the middle term 13 left over, giving 12 × 26 + 13 = 325. The other options arise from arithmetic or pairing errors.
Frequently asked questions
What is the correct answer to this question?
325
Why is this the correct answer?
The numbers from 1 to 25 are the first 25 natural numbers, so the standard sum formula applies: S_n = n(n + 1)/2. Taking n = 25, we get S_25 = 25 × 26 / 2. Since 26 divided by 2 is 13, the product becomes 25 × 13 = 325. Therefore, option B is correct. Pairing the terms also confirms the result: 1 + 25 = 26, 2 + 24 = 26, and so on; there are 12 such pairs, with the middle term 13 left over, giving 12 × 26 + 13 = 325. The other options arise from arithmetic or pairing errors.
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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