Talk:Primary mathematics/Fractions

"2/3 of the students in the class are wearing yellow shirts. 1/4 of the class goes to the library.What fraction of the class is wearing yellow shirts in the library?"

This question is not answerable. — Preceding unsigned comment added by 66.227.211.34 (talk • contribs) 22:36, 12 January 2008 (UTC)

As stated, I agree. However, if we also assume that going to the library and wearing yellow shirts are independent events, then we could use probabilities to answer. The rule there would be to simply multiply the two probabilities, giving us 2/12 or 1/6. If we don't know that the two events are independent, then the best we can do is give a range of from 0% to 25% (the lowest of the two fractions) as the answer. StuRat 06:35, 13 January 2008 (UTC)

To demonstrate further, let's display this in table form, using Y to mean the student is wearing a yellow shirt and L to mean the student is at the library. In the first column is a sample of 12 students, 2/3 of which (8) are wearing yellow shirts. In the second column I randomly assigned the 1/4 of students in the library (3), assuming the two events are independent, in the third column I assigned them assuming that all library students also are wearing their yellow "library lovers" shirt, and in the last column I assumed that the yellow shirts are for "library haters":

Yellow    Is this student presently in the library ?
Shirt ?   Random  "Library Lovers"  "Library Haters"
-------   ------  ----------------  ---------------- 
   Y        L             L               -
   Y        -             L               -
   Y        -             L               -
   Y        -             -               -
   Y        L             -               -
   Y        -             -               -
   Y        -             -               -
   Y        -             -               -
   -        L             -               -
   -        -             -               L
   -        -             -               L
   -        -             -               L
-------   ------  ----------------  ---------------- 
           2/12          3/12            0/12         <- Fraction of 
                                                         total students
                                                         who are both
                                                         yellow shirted 
                                                         and in the 
                                                         library 

StuRat 19:07, 9 June 2008 (UTC)

Wikibooks

I posted this over at the primary mathematics talk page, but just in case anyone doesn't see it there I just wanted to point out that, if anyone thinks this section needs some expanding, we can borrow a lot of necessary material from Wikibooks' Applied Math Basics; the fractions section there is very complete and in-depth. --71.112.145.203 07:12, 8 June 2008 (UTC)

Thanks for the info. StuRat 18:49, 9 June 2008 (UTC)