Subtracting a Larger Fraction from a Smaller Fraction

Date: 01/09/97 at 23:01:25
From: Kevin Byrd
Subject: Subtracting a large fraction from a smaller fraction 

Dr. Math,

My daughter asked me to help her work this problem: 

  19 4/10 - 6 7/10 =

Do we borrow a whole number from 19 so 4/10 now becomes 14/10?
Am I on the right track here?  Is the final answer 12 7/10? 
It has been years... Thanks in advance.

Frustrated,
Kevin Byrd

Date: 01/11/97 at 19:19:32
From: Doctor Lim
Subject: Re: Subtracting a large fraction from a smaller fraction 

Dear Kevin,

Thank you for writing. It is great to hear from parents too. Don't 
worry - you are on the right track and you got the right answer. 

If your daughter does not understand this concept, try making the 
fraction numbers smaller. For example,  

  1 4/10 - 7/10

Then use concrete examples to show her that you cannot take 7/10 away 
from 4/10 - you have to change the 1 whole 4/10 to 14/10.

Slowly bring up the numbers and let her explain to you. You will find 
that once they understand the concept, children like to play teacher 
and explain. The more they explain correctly, the more the concept 
gets "stuck" in their heads and they become more proficient at it.

So keep up the good work !

-Doctor Lim, The Math Forum
 Check out our web site!  http://mathforum.org/dr.math