What is the sum of natural numbers from (15) to (45)?
Answer and explanation
Correct answer: 930
There are \(45-15+1=31\) terms from 15 to 45. The sum of the first and last terms is \(15+45=60\), so the sum is \(\frac{31\times 60}{2}=930\). Although 960 is close, it does not follow from the correct number of terms and average of this sequence. Exam tip: When both endpoints are included, always use \(+1\) while counting the terms.
Frequently asked questions
What is the correct answer to this question?
930
Why is this the correct answer?
There are \(45-15+1=31\) terms from 15 to 45. The sum of the first and last terms is \(15+45=60\), so the sum is \(\frac{31\times 60}{2}=930\). Although 960 is close, it does not follow from the correct number of terms and average of this sequence. Exam tip: When both endpoints are included, always use \(+1\) while counting the 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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