© 2007 M. Tallman

A Mental Math Strategy

© 2007 M. Tallman

94 - 22+ 6

+ 6

100 28- = 72Step 1: 94 is close to 100; 100 is a much easier number to work with.

Step 2: Add 6 to 94 to make it 100.

Step 3: You must also add 6 to 22, which will give you 28.

Step 4: Subtract 28 from 100, mentally.

© 2007 M. Tallman

405 - 97- 5 - 5

400 92- = 308Step 1: 405 is close to 400; 400 is a much easier number to work with.

Step 2: Subtract 5 from 405 to make it 400.

Step 3: You must also subtract 5 from 97, which will leave you 92.

Step 4: Subtract 92 from 400, mentally.

© 2007 M. Tallman

354 - 99+ 1

+ 1

355 100- = 255Step 1: 99 is close to 100; 100 is an easier number to work with.

Step 2: Add 1 to 99 to make it 100.

Step 3: You must also add 1 to 354, which will give you 355.

Step 4: Subtract 100 from 355, mentally.

© 2007 M. Tallman

570 - 285+

15+ 15

585 300- = 285Step 1: 285 is close to 300; 300 is a much easier number to work with.

Step 2: Add 15 to 285 to make 300.

Step 3: You must also add 15 to 570, which will give you 585.

Step 4: Subtract 300 from 585, mentally.

© 2007 M. Tallman

512 - 378- 12 -

12500 366- = 134

Step 1: 512 is close to 500; 500 is a much easier number to work with.

Step 2: Subtract 12 from 512 to make it 500.

Step 3: You must also subtract 12 from 378, which will leave you 366.

Step 4: Subtract 366 from 500, mentally.

© 2007 M. Tallman

A Mental Math Strategy

© 2007 M. Tallman

567

300

- 253

567-267

5026

7-217

221

7-215

215

© 2007 M. Tallman

735

200

- 742

735-535

4053

5-495

749

5-488

488