This is the Important question based on Arithmetic progression Chapter of R.S Aggarwal book for ICSE & CBSE Board.

Here you have to find the

(i) Number of terms so that their sum is Given

(ii)Explain the double answer

Question Number 21 Of Exercise 11 C of RS Aggarwal Solution.

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# Find the number of terms of the AP 64,60,56,……so that their sum is 544. Explain the double answer.

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The given AP is 64,60,56,……………….

We know that,

First term (a) = 64

Common difference = = 60-64 = -4

Given sum of AP () = 544

By using formula:-

⇒

⇒

⇒

⇒

⇒

⇒

⇒ and

⇒ n = 16 and n = 17

so, for the values n=16 and n=17 the sum of the given A.P. is 544.