How can we teach using ten for subtraction?
Edward C. Rathmell
Using a similar procedure for a few minutes everyday for two or three weeks will help nearly all of the class learn to use ten. Besides the routine described in the bullets above, sometimes do the following.
Using make ten for addition will help students learn to use ten for subtraction. It is also important for them to understand the part-part-whole concept and/or comparison situations so that adding from the part to the whole makes sense as a way to solve subtraction problems.
One way to help students learn this strategy is to provide subtraction situations where the whole is greater than ten and one of the parts is eight or nine. Then create a situation where the part that is left after subtracting is hidden. Then as a student is explaining the use ten strategy, you can put counters back with the hidden set as you add on. For example, 9 and 1 more is 10, then 4 more is 14.
Another way to illustrate this thinking is to use a ten frame. If the part being subtracted is close to ten, show it in the ten frame. Then add on as a student explains, 1 more is 10 and 4 more is 14.
The ten frame can also be used by showing the whole in the ten frame. Note that it will fill the ten frame and there will be some extras. Then subtract to ten and subtract the rest from ten as you remove counters from the ten frame.
The number line can also be used. Draw a number line on the board. For 14 - 9, just mark the numbers 9, 10, and 14 on the number line. Then draw arrows as you add to show 9 and 1 is 10, then 4 more is 14. That's 5 more. Or, subtract from 14 to 10, then subtract to 9.