Subtraction in Parts

Using Materials

Problem: “Brian has 14 oranges and eats six of them. How many are left?”
Record 14 – 6 on the board or modelling book. Model 10 and four counters on the tens frames. Ask the students, without them touching the tens frames, to say what remains when six are removed. Invite a student who says that eight is the answer to come and demonstrate how he/she got the answer. Typically, a student removes four from the four frame and then two from the frame with 10 on it to leave eight. Sometimes he/she will remove six from the 10 to leave four and add four and four to give eight. Either method is fine. Record 14 – 6 = 8 on the board or modelling book.
Examples: Word stories and recording for: 15 – 6 20 – 5 16 – 9 12 – 4
20 – 8 11 – 4 13 – 6 ...
Problem: “Tara has $34 and spends $5. How much money does she have left?”
Record 34 – 5 on the board or modelling book. Let the students model 34 with bundled sticks or beans in film canisters. The students break a 10 to get the answer. Discuss how the students get 29.
Examples: Word stories and recording for: 45 – 6 30 – 5 46 – 7 32 – 7
40 – 8 41 – 4 33 – 6 ...

Using Imaging

Shielding: Problem: “Find 43 – 5.”
Record 43 – 5 on the board or modelling book. Model 43 on sticks or beans out of sight of the students. Ask the students to image removing five and describe what is
happening. Fold back, if necessary, to Using Materials. Record 43 – 5 = 38 on the board or modelling book.
Examples: Word stories and recording for: 35 – 7 40 – 9 26 – 8 31 – 5
30 – 8 31 – 3 40 – 7 ...

Using Number Properties

Examples: Word stories and recording for: 75 – 8 90 – 8 96 – 9 61 – 5
70 – 7 51 – 6 81 – 9 ...