Saturday 9 September 2017

SUM OF A GP 1


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

solution

G1 = 2, r=3, n=10

Sn = G1(rn-1)/r-1
               
S10 = 2(310-1)/3-1            

S10 = 12(310-1)/21
               
S10 = (310-1)

S10 = 59049 - 1

S10 = 59048

Hence the sum of the 1st seven terms is 19682.

TRY THIS………………



Find the sum of the 1st eight terms of the geometrical progression 3+9+27+81+…..

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