Unit 3 – Addition and subtraction
2 Try these subtractions. What strategy will you use each time?
(a) 99 − 35 (d) 105 − 17
(b) 84 − 42 (e) 83 − 78
(c) 90 − 60 (f) 200 − 55
Carl adds two numbers. He adds the tens first. There are 12 tens in total. He add the ones next. There are 9 ones in total. What could Carl’s addition be? Find at least five different solutions.
3
E
The children are discussing these addition calculations. 12 + 67 22 + 73 29 + 85
67 + 12 73 + 22 85 + 29
What do you think? What do you notice about the answers to the calculations in the two boxes? Think about how you will represent and communicate your findings to others.
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