NDA2024MathematicsSequences and SeriesActual

The mean of n observations 1,4,9,16, , n^2 is 130 . What is the value of n ?

Options

Correct answer

B. 19

Step-by-step solution

aligned & Mean = 1+4+9+ + n ^2 n & 130= n ( n +1)(2 n +1) 6 n & 780 n = n ( n +1)(2 n +1) & 780=2 n ^2+3 n +1 & 2 n ^2+3 n -779=0 & (2 n +41)( n -19)=0 & x =- 41 2 , 19 & n =19 ( n =- 41 2 not possible ) aligned

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