Question

the first term in a geometric series is 64 and the common ratio is 0.75. Find the sum of the first 4 terms in a series.

Answer 1

hi

u0 = 64       with  u(n+1) = un *0.75  

u3 =  64 *0.75^3   = 27

sum is :      64 *  ( 0.75^4 -1)  / 0.75-1  = 175

manual proof :    64 + 48+36+27 = 175