Question

An arithmetic progression is written in the following way 

The sum of all the terms of the \(10^{th}\) row is ______ .

Answer 1

Correct answer is : 1505 

2, 5, 11, 20, .....

General term \(=\frac{3 n^{2\ }-\ 3 n\ +\ 4}{2}\)

\( \begin{aligned} \mathrm{T}_{10} & =\frac{3(100)-3(10)+4}{2} \\ \end{aligned} \) 

= 137 

10 terms with c.d. = 3 

sum \(=\frac{10}{2}(2(137)+9(3))\) 

= 1505