Tuesday 31 December 2013

SEQUENCE AND SERIES A15

The first term of an AP is 5 and the last term is 57.If the arithmetic progression consists of 20 terms, calculate the sum of all the terms. 

Solution

A1 = 5, n=20, An = 57

Sn = n(A1 + An)
       2

S20 = 20(5 + 57)
         2

S20 = 10 x 62


S20 = 620



Hence the sum of all 23 terms is 620.

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