What is the sum of the first (7) natural numbers?
Answer and explanation
Correct answer: 28
The first 7 natural numbers are \(1,2,3,4,5,6,7\). Their sum is \(1+2+3+4+5+6+7=28\). Using \(S_n=\frac{n(n+1)}{2}\), for \(n=7\), \(S_7=\frac{7\times8}{2}=28\). Note that 21 is the sum of the first 6 natural numbers. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of the first \(n\) natural numbers.
Frequently asked questions
What is the correct answer to this question?
28
Why is this the correct answer?
The first 7 natural numbers are \(1,2,3,4,5,6,7\). Their sum is \(1+2+3+4+5+6+7=28\). Using \(S_n=\frac{n(n+1)}{2}\), for \(n=7\), \(S_7=\frac{7\times8}{2}=28\). Note that 21 is the sum of the first 6 natural numbers. Exam tip: use \(\frac{n(n+1)}{2}\) for the sum of the first \(n\) natural numbers.
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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