Question 962006
{{{matrix(1,22,

common,
ratio,
""="",
r,
""="",
matrix(1,2,2nd,term)/matrix(1,2,1st,term),
""="",
6/8,
""="",
0.75,
""="",
matrix(1,2,3rd,term)/matrix(1,2,2nd,term),
""="",
4.5/6,
""="",
0.75,
""="",
matrix(1,2,4th,term)/matrix(1,2,3rd,term),
""="",
3.375/4.5,
""="",
0.75
)}}}

The formula for the sum to n-terms is

{{{S[n]}}}{{{""=""}}}{{{(a[1](1-r^n))/(1-r)}}}

{{{
matrix(1,4,
where,
a[1],
""="",
matrix(1,11,first,term,""="","8,",r,""="","0.75,", and,n,""="",10)

)}}}

Plugging in:

{{{S[10]}}}{{{""=""}}}{{{(8(1-0.75^10))/(1-0.75)}}}

{{{S[10]}}}{{{""=""}}}{{{30.197967529296875}}} 

Edwin</pre>