Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    stuck on a question guy need help pleeeeeaaaaase! :eek3: :eek3:

    a geometric series has common ratio 0.9. what is the smallest number of terms required for the sum of the series to be greater than 99.9% of the sum of infinity

    any ideas? would like working out too please
    Offline

    2
    ReputationRep:
    Work out the sum to infinity using \Sigma_N =\frac{a}{1-r} where N=infinity.
    Multiply it by 0.99 to get 99%

    Use the equation \Sigma_n=\frac{a(1-r^n)}{1-r}
    to find n, where \Sigma_n is 99% of the sum to infinity.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Has a teacher ever helped you cheat?
    Useful resources

    Make your revision easier

    Maths

    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here

    Equations

    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Write a reply...
    Reply
    Hide
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.