What is the sum of (1+2+3+\cdots+38)?
Answer and explanation
Correct answer: 741
The sum of the first \\(n\\) natural numbers is \\(\frac{n(n+1)}{2}\\). Here, \\(n=38\\), so \\(\frac{38\times39}{2}=19\times39=741\\). Therefore, 741 is correct. The option 760 may result from mistakenly using 40 instead of \\(n+1=39\\). Exam tip: use \\(\frac{n(n+1)}{2}\\) for the sum from 1 to \\(n\\).
Frequently asked questions
What is the correct answer to this question?
741
Why is this the correct answer?
The sum of the first \\(n\\) natural numbers is \\(\frac{n(n+1)}{2}\\). Here, \\(n=38\\), so \\(\frac{38\times39}{2}=19\times39=741\\). Therefore, 741 is correct. The option 760 may result from mistakenly using 40 instead of \\(n+1=39\\). Exam tip: use \\(\frac{n(n+1)}{2}\\) for the sum from 1 to \\(n\\).
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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