Question

In a flower bed, there are 23 rose plants in the first row, 21 in second row, 19 in the third row and so on. There are five plants in the last row. How many rows are there of rose plants ?

Answer 1

Let the number of rows in the flower bed be $n.$

These rose plants form an AP :

$23,21,19,...,5$

Here, $a=23,d=-2,nthterm=5$

$a_n=a+(n-1)d$

$5=23+(n-1)\times -2$

$n-1=9$

$n=10$

Therefore, there are $10$ rows of rose plants.