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Home » In a flower bed, there are 43 rose plants in the first row, 41 in 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?
In a flower bed, there are 43 rose plants in the first row, 41 in 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?
Arithmetic Progression | CBSE | Class 10 | Maths | RS Aggarwal
In a flower bed, there are 43 rose plants in the first row, 41 in 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?

Solution:

The numbers of rose plants in consecutive rows are 43, 41, 39,…, 11.

Difference of rose plants between two consecutive rows = (41 — 43) = (39 – 41) = – 2 [Constant]

So, the given progression is an AP

Here, first term = 43

Common difference = – 2

Last term 11

Let n be the last term, then we have:

= a+(n – l)d

11=43+(n-1)(-2) 11= 45 – 2n

34 = 2n

n =17

Hence, the 17th term is 11 or there are 17 rows in the flower bed.

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