"The Boxing Technique"

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Home : 2004 : September : 25

"The Boxing Technique"
By df

We have been using a "Boxing Technique" for those students that have had difficulty with the concept of subtraction with zeroes.
For an example, let's subtract 234 from 500.
Have students draw a box around the 5 in
the hundreds column and the 0 in the tens column. Leave the 0 in the ones column outside the box.
Using this box frame, they are asked, "What is one less than 50?" (The framed value inside the box).
The answer is 49.
Have them draw the 49 over the boxed frame directly over the correct place value - the 4 over the 5 in the hundreds column, the 9 over the 0 in the tens column.

Tell them to give the "one" to the 0 in the ones column to create a 10.
Now they can subtract.
Make sure they check their work with addition.
I tell my students to draw a box around their answers.

For some reason, many of my students need this sort of visual framework.

In another example...
Subtract 7000 - 678 = ?
Draw a box around the 700 in the thousands column, hundreds column, and tens column.
Ask "What is one less than 700?"
Write 699 above the box over the appropriate place valued numbers. (6 over the seven in the thousands column, 9 over the zero in the hundreds column, 9 over the zero in the tens column.)
Give the "one" to the 0 in the ones column.
Subtract carefully.
Tell the students to always check their answers by adding their answer with the number they subtracted. If they subtracted properly the sum will be the original number - 7000.
Hope this helps.