Question

In a flower bed, there are 43 rose plants in the first row, 41 in the second, 39, in the third, and so on. There are 11 rose plants in the last row. How many rows are there in the flower bed?

Answer 1

In AP form : 43,41,39,37,35......11 (d=-2)

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

11 = 43 +(n-1)-2

11-43 = (n-1)-2

$\frac{-32}{-2}=n-1$

16 + 1=n

n=17

therefore there are 17 rows in the flower bed