Question
Download Solution PDFThe mean of n observations
1, 4, 9, 16 ...., n2 is 130. What is the value of n?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Mean = \(\frac{1+ 4+ 9 ... n^2}{n}\)
⇒ 130 = \(\frac{(n(n+1)(2n+1)}{6n}\)
⇒ 780 = 2n2 + 3n + 1
⇒ 2n2 + 3n – 779 =0
⇒ 2n2 + 41n – 38n – 779 = 0
⇒ n(2n + 41) – 19(2n + 41) = 0
⇒ (2n + 41) (n – 19) = 0
⇒ x = 19 ..... ( n = \(-\frac{41}{2}\) is not possible)
∴ Option (b) is correct.
Last updated on May 30, 2025
->UPSC has released UPSC NDA 2 Notification on 28th May 2025 announcing the NDA 2 vacancies.
-> A total of 406 vacancies have been announced for NDA 2 Exam 2025.
->The NDA exam date 2025 has been announced for cycle 2. The written examination will be held on 14th September 2025.
-> Earlier, the UPSC NDA 1 Exam Result has been released on the official website.
-> The selection process for the NDA exam includes a Written Exam and SSB Interview.
-> Candidates who get successful selection under UPSC NDA will get a salary range between Rs. 15,600 to Rs. 39,100.
-> Candidates must go through the NDA previous year question paper. Attempting the NDA mock test is also essential.