A community for students. Sign up today!
Here's the question you clicked on:
 0 viewing
 2 years ago
Given a geometric sequence whose sum of the first 10 terms is 4 and whose sum from the 11th to the 30th term is 48, find the sum from the 31st to the 60th term.
 2 years ago
Given a geometric sequence whose sum of the first 10 terms is 4 and whose sum from the 11th to the 30th term is 48, find the sum from the 31st to the 60th term.

This Question is Closed

cwrw238
 2 years ago
Best ResponseYou've already chosen the best response.0Sum of 10 = a * (r^4  1)  = 4 r 1

kmeds16
 2 years ago
Best ResponseYou've already chosen the best response.0@cwrw238 why is it r^4? I thought it's r^10.

amistre64
 2 years ago
Best ResponseYou've already chosen the best response.0hmm, given is: \[S_n=\frac{1r^n}{1r}\] \[S_{10}=4=\frac{1r^{10}}{1r}\] \[S_{3010}=48=\frac{1r^{20}}{1r}\]

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2you have been given the sum upto first 10 terms =4 you have also been given the sum upto first 30 terms = 4 + 48 =52 and you have 2 eqns with 2 variables >solve for a and r now calculate sum for first 60 terms from that subtract sum of first 30 terms.. this should help..

hitten101
 2 years ago
Best ResponseYou've already chosen the best response.0dw:1351514867224:dw

kmeds16
 2 years ago
Best ResponseYou've already chosen the best response.0a(r^10  1) / r  1 = 4 a(r^30  1) / r  1 = 52 ? @shubhamsrg like this?

hitten101
 2 years ago
Best ResponseYou've already chosen the best response.0solve for a and r.. then find the sum of 60 terms subtract sum of 30 terms from sum of 60 terms

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2@kmeds16 yep @hitten101 mistake in your formulla in the denominator..

kmeds16
 2 years ago
Best ResponseYou've already chosen the best response.0I got, r^10 = 3. this is confusing :/ 10th root of 3?!

cwrw238
 2 years ago
Best ResponseYou've already chosen the best response.0my mistake r^10 not r^4

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2how'd you get that? o.O

hitten101
 2 years ago
Best ResponseYou've already chosen the best response.0@kmeds16 @shubhamsrg yes no exponent in the denominator.. you are right

kmeds16
 2 years ago
Best ResponseYou've already chosen the best response.0second equation divided by first equation. hehehehehe

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2your main aim is not to find r,, your main aim is to find sum.. leave it as r^10 = 3

kmeds16
 2 years ago
Best ResponseYou've already chosen the best response.0find the sum of S60 and subtract 52, right?

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2do this,,this might simplify.. substitue r^10 =3 whereever you can leave r1 as it is.. you can see a/(r1) = 4/(r^10 1) in calculation for sum of 60 terms ,make use of this eqn,, no need to find a.. :)

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2r^60 we all can find.. hmm.. hope that helped..

kmeds16
 2 years ago
Best ResponseYou've already chosen the best response.0solving...hehehe ahm, thanks for the idea..
Ask your own question
Ask a QuestionFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.