Using Materials

Problem: “At her party, Glynnis provides 67 sweets. At the end of the party, she has 34 left. How many sweets did her guests eat?”

The students model 67 as six tens and seven ones and experiment to see why 34 will be left. The connection the students need to make is that the problem can be solved by working out 67 – 34 or by solving 34 + ? = 67.

Examples: Word stories and recording for: 86 –  ?= 61,  67 – ? = 21, 63 – ? = 17,  500 – ?  = 46 ...

Using Number Properties

Examples: Word stories and recording for: 84 – ? = 61,  77 – ? = 25, 42 – ? = 26,  200 – ? = 156 ...