## Algebra 2 (1st Edition)

For an arithmetic series, the sum for the finite series is given by: $S_n=\dfrac{n(a_1+a_n)}{2}$ Here, $d=6$ From part (a), we have $a_n=6n$ $a_1= 6 (1)=6; a_9=6 \times 9=54$ $S_n=\dfrac{9 \times (6+54)}{2}=270$ Thus, the total sum of the cells in the rings is: $270+1=271$ cells