Q19 of 47 Page 1

How many terms of an A.P. 9, 17, 25, … must be taken to give a sum of 636 ?

As we know sum of A.P

Where, a is first term


d is difference between terms


a = 9, d = 17-9 = 8


Given sum = 636


So,








But n can’t be negative.


So, n = 12


Conclusion: Therefore, 12 terms to be taken for sum to be 638


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