Question

In a flower bed, there are 23 roses plants in the fffitst row, 21 in the second, 19 in the third , and so on .. There are 5 Rose plants in the last row.How many rows are there in the flower bed?

Answer 1

9 is the right answer

Answer 2

The number of rose plants in 1st, 2nd, 3rd,...., rows are : 23,21,19,....5

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

a = 23

d = 21-23 = -2

$a_n=5$

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

5=23+(n-1)(n-2)

-18=(n-1)(n-2)

n=10

So, there are 10 rows on flower bed.