number lines
quick pictures
bar models
standard algorithm
100

count up on the number line

52-46=

6

100

654-213

441

100

show using a bar model

237-126=

111

100

507-158

349

200

count up on the number line 

33-29= 

4

200

673-82

591

200

show using a bar model

232-118=

114

200

300-216

84


300

count up on the number line

88-79= 

9

300

345-116

229

300

show using a bar model

532-____=319

213

300

404-125

279

400

count up on the number line

40-29=

11

400

129-113

16

400

show using a bar model

436-____=217

219

400

200-155

45

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