Expert: Chanda Walker - 3/17/2009

Question
Use the numbers 1, 2, 3, 4, 5, and 6 to write a subtracion problem with two mixed numbers that have a difference of 4 13/20.

Answer
Edit to add:

I couldn't sleep until I figured this out.

6 2/5 - 1 3/4
5 28/20 - 1 15/20
4 13/20


I used all the numbers just once.

Sorry about the hiccup.  It is late.  I have no other excuse.


Can I use the numbers more than once?  

Well let me attack it.

I want something that will cause me to need a least common denominator of 20.  I'll use the 4 and 5.

/4 - /5

If I want a difference of 4 whew I better make a big number and a small number.

6 ?/4 -  2 ?/5

Ok that is just bigger than 4 but what for the ?'s.

6 3/4 will go to 6  15/20

I need to subtract 2 from that 15 and I need a number that is a multiple of 4!  Hmmm how about a borrow?

6 1/4 will go to 5 25/20

so I'll need to subtract 12 from that 25 AHA that is a multiple of 4!

1 3/5 will go to 1 12/20

Ok I think that is it!

6 1/4 - 1 3/5
= 5 25/20 - 1 12/20
= 4 13/20

Hey!  That is it!  BUT I used 1 twice.  Is that bad?

I'll keep thinking on this.  If I figure it out, I'll revise my answer.  Maybe I've given you enough clues to figure it out without me?