Answer
271 cells
Work Step by Step
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
