My kid comes to me with the following problem and says she doesn't know how to do that "math."
ten years ago A was three times as old as C this year A is 50 years older than C. how old is A i go to explain to her that this isn't as much a "math" mystery as it is a problem of defining terms and applying logic. The problem asks us to solve for: the current age of A there are two statements, the subject of which are: 1. the ages of A and C ten years ago 2. the ages of A and C today the problem with solving this question is that people who look at it as a math problem might only see two variables, A and C. there are, however, 4 variables: A(age 10 years ago) or Asub10 C (age 10 years ago) or Csub10 A(age today) or let's just call this A C (age today) or let's just call this C The two statements are saying the following: Asub10=3*Csub10 A-50=C however, as we know by definition the relationship between these variables and can therefore reduce them to two. A-10=Asub10 C-10=Csub10 so the first statement can be expressed A-10=3(C-10) therefore: A-10=3C-30 therefore: A=3C-20 and We also know that: A-50=C therefore: A=C+50 Now we have defined A in terms of two statement about C, that A is both: C+50 and 3C-20 since both of those are the same as A and A is the same as A it follows that C+50=3C-20 therefore 50=2C-20 therefore 2C=70 So we know that C is 35 based the statement A-50=C then A-50=35 which means A=85 if we plug it into our other statement, we can check that A=85 if and only if C=35, so we can be confident that A=85 My kid looks at me like I'm mad and says "ok, so you are sure that A is 85 years old, right". i explain that it seems to be a logical certainty and she should see that from the demonstration. to which she replies "well, ok, if you are sure, then i'll use that" I somehow think a boy might have done better with this -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20090616/cf4f84be/attachment.html> _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
