Question 82098
find the common ratio of an infinite geometric series with first term 6 and with sum 7.5
The formula for finding the sume of an infinite series is:  {{{highlight(S=a/(1-r))}}}, where S is sum, a is the first term, and r is the common ratio.
In your case, S=7.5 and a=6
{{{7.5=6/(1-r)}}}
{{{7.5(1-r)=6/(1-r)*(1-r)}}}
{{{7.5-7.5r=6}}}
{{{7.5-7.5-7.5r=6-7.5}}}
{{{-7.5r=-1.5}}}
{{{-7.5r/-7.5=-1.5/-7.5}}}
{{{highlight(r=1/5)}}} or in decimal form {{{highlight(r=.2)}}}
Happy Calculating!!!!