Created by Paula Cantera Elk Neck Elementary

The Left-to-Right Algorithm forSubtraction builds on a skill mostpeople use every day -- readingfrom left to right.

First, some vocabulary.

857469-

minuendsubtrahend388 difference

(top number)

(bottom number)

(the answer)

Let’s begin. First think of thesubtrahend (the bottom number)in expanded form - like this…

857469-400 + 60 + 9

857469-

857

400

Now subtract the hundreds.

+ 60+ 9

- 400457

857469-

857

400

Next subtract the tens.

+ 60+ 9

- 400457- 60397

857469-

857

400

Finally subtract the ones.

+ 60 + 9

- 400457- 60

397

388- 9

8 17

857469-

857

400

388 is the difference!

+ 60 + 9

- 400457- 60

397

388- 9

8 17

Let’s try another one that mightbe a bit harder.

Are you up for the challenge?

5642- 1076100

0+ 70+ 6

+ 0

Notice that there are no hundreds in the number1076.The number can be expanded in either ofthe two ways shown above.

or

Expanded form 1000

+ 70+ 6

***ALERT***

5642- 1076

1000

+ 70+ 6

5642- 10004642- 70

5 14

4572- 6

6 12

45664566 is the difference!

Subtract the thousands.

Subtract the tens.

Subtract the ones.

The Left-to-Right Algorithmfor Subtraction is just one more way to subtract multi-digit numbers.

Go ahead!Give it a try!It might justbecome your favorite!