As mentioned in the previous post, my favorite tool to help children learn place value concepts is a plastic Unifix tray showing the 100s, 10s and 1s places. To show simple subtraction, start with a few simple math facts such as 9-1. Have the child show 9 cubes and place them in the 1s column of the tray. Ask them to subtract 1 of these, and they will see 8 ones are left.
HOW TO DO THIS WITH A DOUBLE DIGIT FACT
Using place value to show 10-5, or 12-6, or 10-9: Children first need to represent the 2-digit number 10 as 1 ten and zero ones, or the 12 as 1 ten and 2 ones.
TO SHOW 14-5=9
This next photo shows 14 as 1 ten and 4 ones.
EXCHANGE 1 TEN FOR 10 ONES
In order to subtract 5 ones, first an exchange has to happen. I ask the child to hand me the 1 ten, and how many ones are in a ten. As I hand them back ten different color Unifix cubes, I remind them that these are ones, and to place them in the 1s place in the tray. Of course, the ten 1s won't fit, but that's okay.
Next, the child counts to see that there are now 14 ones in the 1s place. (4+10 = 14). They can complete the subtraction problem. 14 (ones) - 5 leaves 9. Once they see why 14-5=9, then they are ready to memorize the math fact. Two Plus Two Is Not Five has all the strategies, tips and practice pages you need to help your students learn and memorize addition and subtraction facts.
Finally, try this for several different math fact problems such as 12-6, 10-9, and 14-7.
More posts will follow with place value. Adding and subtracting with 2-digit numbers, with and without regrouping, and on to the 100s place. Can't wait? Beyond Math Facts offers instruction and many reproducible practice pages, and is available at many stores, and at online vendors, or you can buy directly from our Buy page. See the sample pages on this website! Word math is also included in this unique workbook.
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