10. Five marks example problems III

The \(13^{th}\) term of an A.P. is \(3\) and the sum of first \(13\) terms is \(234\). Find the common difference and the sum of the first \(21\) terms.

 

Common difference \(=\) $\frac{i}{i}$

 

The sum of first \(21\) terms \(=\)