Using the 100's Chart for Add and Subtraction

Using the 100's Chart for mental math addition and subtraction

I have had several parents wonder whats going on in math lately, our mental math unit is attempting to show our students how to add and subtract using a 100's chart.

Using the 100's Chart for mental math addition and subtraction

To add two numbers using "mental math", we have to remember several steps:

34 + 25 = 

1. Locate 34  then ,
2. realize that 25 is two tens and 5 ones
3. tens travel on the 100's chart by being the next number under the beginning number. For example 44,54
4. Now you have 5 ones travel right on the chart...55,56,57,58,59
5. The answer to 34 + 25 =  is 59

Let's try subtracting!

53 - 27 =

1. locate 53
2. realize that 27 is 2 tens and 7 ones
3. so we move up the column from 53
4. 43,33
5. and now move 7 ones left from 33
6. 32,31,30,29,28,27,26
7. 26 is the answer

We still haven't taught our kids how to subtract by "borrowing" or add by "carrying" yet...however even that's been changed to "regrouping"....lol...

Thanks Parents and Readers for all you do with your kids....

Mr. F