Question

In a Flower bed There are 23rose plants in the first row 21in the second,19in the third and so there are 5rose plants in the last row. how many rows are there in the flowerbed

Answer 1

This is the form of A.P.

a=5
an=23
d=23-21
=2
n=?

an=a+(n-1) ×d
23=5+(n-1)× 2
23-5=2n-2
18+2=2n
20=2n
n=20÷2
n=10