Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    I am doing a past paper about compound interest. I know its easy but i just simply can not understand this for some reason.

    Question:
    Jaspir invested £2400 for n years in a savings account.
    He was paid 7.5% per annum compound interest

    At the end of the n years he had £3445.51 in the savings account

    b) Work out the value of n

    My workings:

    Well i got the equation for Compound interest : Total = P x (1+x) ^n

    Then i substituted: 2400 x (1.075)^n = 3445.51

    Expanded and tried to get n on its own : 1.075^n - 3445.51 / 2400


    How do i get n on its own?


    Thanks

    -JFinzz
    Offline

    14
    ReputationRep:
    (Original post by JFinzz)
    I am doing a past paper about compound interest. I know its easy but i just simply can not understand this for some reason.

    Question:
    Jaspir invested £2400 for n years in a savings account.
    He was paid 7.5% per annum compound interest

    At the end of the n years he had £3445.51 in the savings account

    b) Work out the value of n

    My workings:

    Well i got the equation for Compound interest : Total = P x (1+x) ^n

    Then i substituted: 2400 x (1.075)^n = 3445.51

    Expanded and tried to get n on its own : 1.075^n - 3445.51 / 2400


    How do i get n on its own?


    Thanks

    -JFinzz
    How did you get 3445.51
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by steve2005)
    How did you get 3445.51
    It was in the question. That was his compound interest after the n years
    Offline

    2
    ReputationRep:
    (Original post by JFinzz)
    I am doing a past paper about compound interest. I know its easy but i just simply can not understand this for some reason.

    Question:
    Jaspir invested £2400 for n years in a savings account.
    He was paid 7.5% per annum compound interest

    At the end of the n years he had £3445.51 in the savings account

    b) Work out the value of n

    My workings:

    Well i got the equation for Compound interest : Total = P x (1+x) ^n

    Then i substituted: 2400 x (1.075)^n = 3445.51

    Expanded and tried to get n on its own : 1.075^n - 3445.51 / 2400


    How do i get n on its own?


    Thanks

    -JFinzz
    For this, you don't actually need to get n on its own, you just need to keep applying the compound interest to the values at the end of each year until you get 3445.51. Then the number of times you had to do this is your value for n.
    Offline

    4
    ReputationRep:
    I can't remember if logs is GCSE or not, if it isn't simply use trial and error to see what value of n makes 1.075^n = 3445.51/2400
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by JFinzz)
    Then i substituted: 2400 x (1.075)^n = 3445.51
    This is right.

    Divide both sides by 2400 to obtain.

    1.075^n = 1.435629...

    Try integer values of n in order. It won't take you long.
    Offline

    1
    ReputationRep:
    log 1.425 / log 1.075
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 10, 2011
The home of Results and Clearing

3,613

people online now

1,567,000

students helped last year

University open days

  1. SAE Institute
    Animation, Audio, Film, Games, Music, Business, Web Further education
    Thu, 16 Aug '18
  2. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  3. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
Poll
Will you be tempted to trade up and get out of your firm offer on results day?
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

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.