What is the sum of (23+24+25+\cdots+34)?
Answer and explanation
Correct answer: 342
There are \(34-23+1=12\) terms from 23 to 34. This is an arithmetic progression, so its sum is \(\frac{12}{2}(23+34)=6\times57=342\). Therefore, 342 is correct. A value such as 352 can result from an error while counting the terms or finding the average. Exam tip: for consecutive numbers, add the first and last terms and multiply by half the number of terms.
Frequently asked questions
What is the correct answer to this question?
342
Why is this the correct answer?
There are \(34-23+1=12\) terms from 23 to 34. This is an arithmetic progression, so its sum is \(\frac{12}{2}(23+34)=6\times57=342\). Therefore, 342 is correct. A value such as 352 can result from an error while counting the terms or finding the average. Exam tip: for consecutive numbers, add the first and last terms and multiply by half the number of 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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