How much is the sum of the first (90) natural numbers?
Answer and explanation
Correct answer: 4095
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=90\), we get \(\frac{90\times91}{2}=45\times91=4095\). Therefore, \(4095\) is the correct answer. A value such as \(4085\) may result from a small multiplication or division error. Exam tip: Cancel the even factor with 2 before multiplying \(n(n+1)\).
Frequently asked questions
What is the correct answer to this question?
4095
Why is this the correct answer?
The sum of the first \(n\) natural numbers is \(\frac{n(n+1)}{2}\). Substituting \(n=90\), we get \(\frac{90\times91}{2}=45\times91=4095\). Therefore, \(4095\) is the correct answer. A value such as \(4085\) may result from a small multiplication or division error. Exam tip: Cancel the even factor with 2 before multiplying \(n(n+1)\).
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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