How much is the sum of natural numbers from (31) to (40)?
Answer and explanation
Correct answer: 355
There are 10 numbers from 31 to 40, inclusive. They form an arithmetic progression, so the sum is \\(\frac{10}{2}(31+40)=5\times71=355\\). Getting 345 indicates an error in counting the terms or using the last term. Exam tip: When finding the sum over an inclusive range, count both endpoints.
Frequently asked questions
What is the correct answer to this question?
355
Why is this the correct answer?
There are 10 numbers from 31 to 40, inclusive. They form an arithmetic progression, so the sum is \\(\frac{10}{2}(31+40)=5\times71=355\\). Getting 345 indicates an error in counting the terms or using the last term. Exam tip: When finding the sum over an inclusive range, count both endpoints.
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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