Expert: Lynn Houston - 10/4/2010

Question
3 5/8-5/6.  I found the comon denomiator as 24 but when I worked it out by subtracting the numeratot, I got a negative nummber.  I know you need to borrow from the whole number as three but not sure where to go from there.  

Answer
You can do it one of two ways, convert the mixed fraction to a fraction, find common denomitor and then subtract, or, if you just want to "borrow" from the 3, you do it like this...

3 5/8 - 5/6      switch to common denominator
3 15/24 - 20/24

Ok, so to "borrow" from the 3, 24/24 = 1, so if you take one from the 3 to add to the 15/24, you get 2 39/24 - 20/24 = 2 19/24.

By borrowing, you're dealing with smaller numbers and skipping some math.  The other way is to turn 3 5/8 in a fraction, which is 29/8, then find the common denominator, subtract and then reduce again.

29/8-5/6
87/24 - 20/24
67/24 = 2 19/24



Make sense?