Question

In a flower garden, there are $23$ plants in the first row, $21$ plants in the second row, $19$ plants in the third row and so on. If there are $10$ rows in that flower garden, then find the total number of plants in the last row with the help of the formula $t_n=a+(n-1)d$.

Answer 1

Here , the A.P of sequence is $23,21,19.....$
$a=23$ , $d=-2$ ,$n=10$
So as we know
$t_n=a+(n-1)d$
$t_n=23+(10-1)(-2)$
$t_n=23+\left(9\right)(-2)$
$t_n=23-18$
$t_n=5$
There are $5$ plants in last row.