Wouldn't it be nice if all numbers you needed to subtract from another number ended in 0, 5 or even a 1 or 2? It would, but in reality numbers can vary and almost always do; especially when you are trying to do the calculations in your head. Working in a job that deals with money and giving change I have become very fond of the count-on method. It works so well, and is almost fail proof when you do it right! And the best part about it is you always have the necessary equipment needed to use this method; your fingers!
Lets start with an easy example: 729 - 400=? To start we count on our fingers up from 400. 500, 600, 700 so we have 3 hundreds. Then we count up the tens place which would be 10, 20 giving us 2 tens. Finally we count up from the ones place which is 0 up to 9 giving us 9 in the ones place. Then we have our answer of 329.
Another way to describe it would be using an example of giving someone change. Lets say the total bill is $7 and they pay with a $10. So you count back the total change by using your fingers or the count-on method; 8, 9, 10. The change would be $3 dollars.
There also is another method similar to the count-on method, it is the count-back method. It basically works like the count-on method only you start with the smaller number and add onto it until you reach the total. An example of this is: 293-80=? So to start there are no hundreds in this example so you have 200. Then you see that there 9 tens minus 8 tens which equals 10 tens. Finally there are 3 ones minus 0 ones which equals 3. So your total left is 213.
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