Thursday 10 July 2014

SUM OF A GP 1

Find the sum of the 1st seven terms of the geometrical progression 2+6+18+54+…….

solution

G1 = 2, r=3, n=7

Sn = G1(rn-1)/r-1
               

S7 = 2(37-1)/3-1
             

S7 = 12(37-1)/21
              

S7 = (37-1)

S7 = 2187 - 1

S7 = 2186

Hence the sum of the 1st seven terms is 2186.

TRY THIS………………


Find the sum of the 1st six terms of the geometrical progression 7+14+28+56+…..

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