Addition
Subtraction
Rounding
Estimate
Strategies
100

987987+7897=

995,884

100

There were 396,123 items. Then 127,288 of them were sold. How many were NOT sold?

 396,123

-127,288

__________

268,835

100

9179 to nearest hundreds

9200

100

estmate to solve 287+558

300+600=900

100

I can use this strategy by only writing the numbers and operation down on my paper (working it out with pencil and paper).

Algorithm

200

7990+4399=

12,389

200

80,000-5,299=

74,701

200

9259 to nearest tens

9260

200

estimate to solve 1200+1600

1000+2000+3000

200

If I want to make units, rods, and flats on my paper, the strategy I am using is....

Draw a picture/model

300

789+276=

1,065

300

170-89=

81

300

1050 to nearest hundreds

1100

300

estimate 

280 +182

300+200=500

300

I can figure out the answer by changing 325 plus 259 to: 300+200+20+50+5+9=

Decomposing numbers (break it down)

400

2397+8113=

10,510

400

51082-17176=

33,906

400

4593 to nearest thousands

5000

400

estimate to solve 805+412

800+400=1200

400

I can do this problem in my head like on mad minute.

mental math

500

1667+1995=

3,662

500

700-250=

450

500

17809 to nearest thousands

18,000

500

345+780=

300+800=1100

500

I can use this strategy when i have the total and one part. or if I have 2 parts and need the whole.

Strip Diagram