Help please? Will fan and medal !

Question

xaze · Answer

Diana received 65 points on a project for school. She can make changes and receive three-tenths of the missing points back. She can do this 10 times . Create the formula for the sum of this geometric series, and explain your steps in solving for the maximum grade Diana can receive.

anonymous · Answer

first correction she gets 35(3/10
 second correction she gets 35(3/10)^2
third correction she gets 35(3/10) ^3 
And so on
Added together we get  ∑ 35(3/10)n+1 as n goes from 0 to ∞
 
35(3/10) ∑ (3/10)n
 
the sum of an infinite geometric series is a/(1-r) which in this case is 1/(7/10) = 10/7
 
35(3/10)(10/7) = 15
 
So maximum grade is 65 + 15 = 80
 
The series was converging because 0 < r < 1

xaze · Answer

@_greatmath7, Thank you very much, you're truly a life-saver! Granted you your medal... think you can help with a few more? ^^

anonymous · Answer

yep

anonymous · Answer

of course

xaze · Answer

Thanks! But I'll go ahead and post it as a new question, so I can give you more medals, haha ^^

anonymous · Answer

u don't have to but thanks. :)