Math
posted by Max .
Calculate the sum of the infinite series 72 + 60 + 50 + 125/3 + ...
489
432
360
307
Can someone please help me with this one? I can never solve these on my own:(

Math 
bobpursley
if it is geometric, r=60/72=10/12=5/6
adn then 5/6(60=50
and then 40(5/6)=200/6=100/3, so that is not a geometric series. Did your teacher make an error? Lets test if she meant it to be a geometric series, r=5/6
sum=72/(15/6)=72*6=amazing, the answer is there.
So I bet your teacher meant 100/3 as the fourth term. 
Math 
Max
Oh ok, thank you so much.

Math 
Steve
Nah. Where did you get the 40? 50 * 5/6 = 250/6 = 125/3
so, you have a genuine GP, with
a = 72
r = 5/6
So, S = 72/(1  5/6) = 72*6 = 432
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