Don't Subtract - Add!
Solve subtraction problems by using addition.
Number Framework Stage 6
Problem: Moana has $63 and gives Miles $59. How much does Moana have left?
Students pair off. One student acts as Moana. She gets $63 as 6 tens and 3 ones. The other student is to be paid $59. They discuss how this can be done. Usually Moana would give Miles 5 tens. Then Moana has to realise she must swap the remaining ten dollar note for ten ones. Then have a group discussion. Discuss the solutions to 63 - 59 and 59 + ? = 63. Why are both answers the same? Examples. Solve and record the answers for: 80 - 78, 83 - 77, 63 - 57, 33 - 26, 50 - 49, 23 - 18..
Using Imaging
Shielding: Problem: Work out 92 - 87.
Shield $87 and ask the group of students how many are required to make $92. Discusswhy you have added $3 to $87 to make $90 then added $2 more to make $92. So the answer is 5. Discuss the link to 92 - 87. Fold back and show the material if needed. Record the answer on the board.
Using Number Properties
Problem: 73 - 28.
Discuss why this problem is the same as 28 + ? = 73
Examples. Solve and record the answers for: 81 - 18, 75 - 39, 93 - 57, 103 - 88, 110 - 89, 64 - 38…
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