SUBTRACT WITH NUMBER LINE MODELS INSTRUCTIONS

The following image was made by Subtract Fractions Designer:

The parts of a subtraction example are the minuend, the subtrahend, and the difference.

When the program starts, you will be asked to identify the minuend and then the subtrahend. The program will continue when the minuend and subtrahend are correctly identified. You will then be asked to find the difference.

You can see from the picture that the minuend is 3 1/2 units in length and the subtrahend is 2 4/5 units in length. The difference will be the distance from the end of the subtrahend to the end of the minuend for 7/10 units.

In many examples, the difference may be found visually by determining the distance from the end of the subtrahend to the end of the minuend. In the above example, add the 1/2 after the whole number 3 in the minuend to the 1/5 before the whole number 3 in the subtrahend for a difference of 7/10.

When the numerator of the subtrahend is larger than the numerator of the minuend you may rewrite the minuend to subtract. Some texts call the procedure "borrowing". To borrow, simply decrease the whole number 3 by 1. Then add 10/10 to 5/10 to get 15/10, giving the fraction 2 15/10.

Notice how 3 5/10 is renamed as 2 15/10 so that the numerators can be subtracted.

Another method would be to first write the minuend and subtrahend in fraction form. The example would look like this:

Or you may prefer to work vertically. Notice in this example the fractions are first written with a common denominator but the minuend 3 5/10 is written as 2 15/10.