Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

Session 4, Part C:
Colored-Chip Models

In This Part: Addition | Subtraction | Multiplication | Division

When doing subtraction using this model, you cannot take away things that are not present. Adding pairs of zeros gives us the actual pieces we need to take away. This can be shown symbolically as follows: +6 - (-4) = (6 + 4) - (4 + -4) = 10 - 0 = 10. Notice that +4 was added to both numbers, which is the same as adding and subtracting 4. Note 10

 • To find the difference of +3 - (+1), begin with three black chips (three positives). Subtract one black chip (one positive). Record what is left (two positives, or +2): • To find the difference of -5 - (-2), begin with five red chips (five negatives). Subtract two red chips (two negatives). Record what is left (three negatives, or -3): • To find the difference of +4 - (+6), begin with four black chips (four positives): Your next step would be to subtract six black chips (six positives), but there are not enough black chips to subtract six. So put in zeros (pairs of positives and negatives) until there are enough black chips to subtract six: (Note that the collection is still worth four black chips.) Now subtract six black chips, and record what is left (two negatives, or -2): • To find the difference of +2 - (-3), begin with two black chips (two positives): Since there are no red chips to subtract, put in zeros (pairs of positives and negatives) until there are enough red chips to subtract three: (Note that the collection is still worth two black chips.) Now subtract three red chips, and record what is left (five positives, or +5): Draw or make a diagram to show the colored-chip model for each of the following:

Problem C3

+5 - (-6)

 Problem C4 -5 - (-6)

 Session 4: Index | Notes | Solutions | Video