First and last terms are provided

Algebra Level 3

An Arithmetic Progression 12 , A 1 , A 2 , A 3 , … , A n − 1 , A n , 19 12, A_1, A_2, A_3,\ldots, A_{n-1}, A_n, 19 is such that ∑ i = 1 n A i = 2015 \sum_{i = 1}^{n}A_i = 2015 . Find n n .


The answer is 130.

Rajen Kapur by Rajen Kapur , 72, India

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1 solution

Pulkit Gupta
Dec 7, 2015

The sum of n arithmetic means is n * ( first term + last term)/2.

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