What is the sum of (16+17+18+\cdots+25)?
Answer and explanation
Correct answer: 205
These are 10 consecutive natural numbers from 16 to 25. Their average is \(\frac{16+25}{2}=20.5\), so the sum is \(10\times20.5=205\). A value such as 195 can result from counting the number of terms or the average incorrectly. Exam tip: for consecutive terms, first count them using \((25-16+1)\).
Frequently asked questions
What is the correct answer to this question?
205
Why is this the correct answer?
These are 10 consecutive natural numbers from 16 to 25. Their average is \(\frac{16+25}{2}=20.5\), so the sum is \(10\times20.5=205\). A value such as 195 can result from counting the number of terms or the average incorrectly. Exam tip: for consecutive terms, first count them using \((25-16+1)\).
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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