1. Not finding help here? Sign up for a free 30min 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!

Some Discreet Math stuff

  1. Mar 29, 2007 #1
    1. The problem statement, all variables and given/known data

    Two mail carriers meet on the route and have a conversation
    A: You have three sons. How old ar ethey?
    B: if you multiply their ages, the result will equal your age
    A: That's not enough to tell me the answer!
    B: the sum of these three numbers equals the number of windows in that building.
    A: But it's still not enouhg!
    B: My middle son is red-haired
    A: Ah, now it's clear!"
    How old are the sons?

    2. Relevant equations


    3. The attempt at a solution

    I tried just plugging a bunch of three setted numbers but i just don't know what the hell i'm tryin to go for. I can deduce from the red-haired part that there are no twins at all in the three kids so the numbers have to be unique but besides that I've gotten nowhere!
  2. jcsd
  3. Mar 29, 2007 #2
  4. Mar 29, 2007 #3
    Assuming people don't live more than 100 years, the age of mail carrier A is less than or equal to 100 so the product of mail carrier B's son's ages is less than or equal to 100.

    Also, since most building are rectangular in nature, the number of windows will normally be the product of two numbers (what do these numbers represent?).
  5. Mar 29, 2007 #4


    User Avatar
    Staff Emeritus
    Science Advisor

    The importance of "My middle son is red-haired" is that there IS one "middle son". Look at the sets of 3 numbers that satisfy the conditions and see if there is only one that does not have 3 distinct numbers.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Some Discreet Math stuff