Results are out! Find what you need...fast. Get quick advice or join the chat
Hey! Sign in to get help with your study questionsNew here? Join for free to post

Algebra with fractions

Announcements Posted on
Applying to uni this year? Check out our new personal statement advice hub 28-11-2014
    • Thread Starter
    • 4 followers
    Offline

    ReputationRep:
    I have to find out what n equals for the equation below:
    \frac{1}{2n}+\frac{1}{3n}=7
    I'm confused on how I start off. This is mainly because of n being the the denominator. :confused:
    • 3 followers
    Offline

    ReputationRep:
    Think about what would happen if you were to multiply both sides by something?
    • Thread Starter
    • 4 followers
    Offline

    ReputationRep:
    Do you mean by 6n as it's the LCM of 3n and 2n? or by just 6?
    • 1 follower
    Offline

    ReputationRep:
    (Original post by krisshP)
    I have to find out what n equals for the equation below:
    \frac{1}{2n}+\frac{1}{3n}=7
    I'm confused on how I start off. This is mainly because of n being the the denominator. :confused:
    You need to put it all over a common denominator e.g. 6n like you suggested it can't just be six a 'n' is also a common factor between the two. LCM is exactly right
    • Thread Starter
    • 4 followers
    Offline

    ReputationRep:
    (Original post by books28)
    You need to put it all over a common denominator e.g. 6n like you suggested it can't just be six a 'n' is also a common factor between the two. LCM is exactly right
    Okay. I understand why I have to make 6n be the denominator. But how do I do that. The fact that the 2n and 3n are the denominators puts me off and makes it all hard for me.
    • 365 followers
    Offline

    ReputationRep:
    \frac{1}{2n}=\frac{3}{6n}

    Does that help?
    • 365 followers
    Offline

    ReputationRep:
    Sophie's suggestion is easier by the way!
    • Thread Starter
    • 4 followers
    Offline

    ReputationRep:
    I think I worked it out but I'm not sure:
    \frac{1}{2n}+\frac{1}{3n}=7
    I multiply both sides by 3n, giving the following:
    \frac{3n}{2n}+1=21n
    I minus 1 from both sides to give the following:
    \frac{3n}{2n}=21n-1
    the Ns on the faction cancel out to give:
    \frac{3}{2}=21n-1
    This causes in a different form:
    1.5=21n-1
    Adding 1 to both sides provides:
    2.5=21n
    Then dividing both sides by 21 to get n on its own gives:
    0.119047619047619047619047619047  62 = n

    Is this a right method or not?
    • 2 followers
    Offline

    ReputationRep:
    1/2n+1/3n=7
    1/2*1/n+1/3*1/n=7
    (1/2+1/3)*1/n=7
    You finish it off.
    • 365 followers
    Offline

    ReputationRep:
    (Original post by krisshP)
    Then dividing both sides by 21 to get n on its own gives:
    0.119047619047619047619047619047  62 = n

    Is this a right method or not?
    Yes but horribly long winded. Can you use fractions rather than decimals?

    Easier would be just to multiply by 6n.
    • Thread Starter
    • 4 followers
    Offline

    ReputationRep:
    so answer is 2.5/21
    Thanks!
    • 365 followers
    Offline

    ReputationRep:
    (Original post by krisshP)
    so answer is 2.5/21
    Thanks!
    Have you ever seen a fraction that looks like that?
    • 3 followers
    Offline

    ReputationRep:
    (Original post by krisshP)
    so answer is 2.5/21
    Thanks!
    It's 5/42.
    • Thread Starter
    • 4 followers
    Offline

    ReputationRep:
    I know. sorry. My clumsy mistake

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: April 15, 2012
New on TSR

Vote for your favourite Christmas film

Win a bundle of Xmas DVDs

Article updates
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.