Question 987851
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It is an arithmetic progression with the first term  {{{a[1]}}} = 50,  the common difference  1  and the number of terms is  (84-49) = 35.


Apply the formula for the sum of first &nbsp;<B>n</B>&nbsp; terms of an arithmetic progression

(see, for example, the lesson &nbsp;<A HREF=http://www.algebra.com/algebra/homework/Sequences-and-series/Arithmetic-progressions.lesson>Arithmetic progressions</A>&nbsp; in this site).


S = {{{(a[1]+a[n])/2*n) = {{{(50+84)/2*35}}} = {{{(134/2)*35}}} = 67*35 = 2345.