Answer :
The sum of a geometric sequence is:
s(n)=a(1-r^n)/(1-r), a=initial term and r=common ration so
s(n)=20(1-0.25^n)/(1-0.25)
s(5)=20(1-0.25^5)/(0.75)
s(5)=26.640625
s(n)=a(1-r^n)/(1-r), a=initial term and r=common ration so
s(n)=20(1-0.25^n)/(1-0.25)
s(5)=20(1-0.25^5)/(0.75)
s(5)=26.640625