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The students of the school are arranged in 20 rows.The number of students in each rows greater than the number of students in proceeding row by a fixed number.The total number of students in the last row and first row is 124. a}find the total number of students in 5th and 16th row.? b)find the total number of students altogether in 200 rows?
This is an arithmetic progression.
The numbers in each row are a , a+d , a+2d, . . . ,a+19d
where a is the number of students in first row and d is the fixed number.
Given that a + a+ 19d = 124
ie, 2a + 19d = 124   .........(i)
number of students in 5 th row = a + 4d and
number of students in 16 th row = a + 15d
Their sum = a + 4d + a+ 15d
                = 2a + 19 d
                 = 124 (from (i))
 


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