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Example 10 - In a flower bed, there are 23 rose plants - Examples

Example 10 - Chapter 5 Class 10 Arithmetic Progressions - Part 2

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Example 10 In a flower bed, there are 23 rose plants in the first 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? Given, Rose plants in 1st , 2nd , 3rd rows are: 23, 21, 19, ………., 5 Since Difference between consecutive terms is same, it is an AP We have to find number of row in the flower bed Lets assume there are n rows in the flower bed Here, an = 5 , a = 23 & d = 21 – 23 = –2 Putting these values in the formula an = a + (n – 1)d 5 = 23 + (n – 1) ( –2) 5 = 23 – 2n + 2 5 = 23 – 2n + 2 5 = 25 – 2n 2n = 25 – 5 2n = 20 n = 20/2 n = 10 So, there are 10 rows in the flower bed .

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.