1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stuck on a homework question

  1. Feb 14, 2008 #1
    Okay so there are four numbers represented by A,B,C,D. Their sums when adding three of the four equal the following sums.. 20,22,24, and 27. This is what I have discovered so far but am really stuck.

    a+b+c+d=x 20= b+c+d or 20= x-a 22=x-b 24= x-c 27=x-d

    Thanks in advance to anyone who can solve this, I really appreciate it!!
  2. jcsd
  3. Feb 15, 2008 #2


    User Avatar
    Science Advisor

    First, you should be aware that there is a homework forum and I am going to move this thread there.

    Second, the 4 3-member subsets of {A, B, C, D} are {A, B, C}, {A, C, D}, {A, B, D}, and {B, C, D}. You have 4 equations: A+ B+ C= 20, A+ C+ D= 22, A+ B+ D= 24, and B+ C+ D= 27. You should be able to solve 4 equations for the 4 unknown numbers. There is no need to introduce a fifth, "x".
    Those should be easy to solve. For example, from the first equation, A= 20- B- C. Replace A in the other 3 equations and you have reduced form 4 to 3 equations. Keep doing that.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Stuck on a homework question