Cleo the time traveller is in prehistoric times with her friend Blake. They are exploring around the dinosaur world and need your help to subtract 2-digit numbers.
More resources for Autumn Block 2 Step 13.
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Discussion points for teachers
1. Help them to work out how many are left.
Discuss how many eggs there were to begin with. Discuss how many are broken? Discuss how the bar model can be used to help?
58 – 16 = 42 whole eggs left
2. Help Cleo and Blake to work out how many adult stegosauruses there could be.
Discuss how there could be more than one answer to this question. Discuss how many dinosaurs there could be in total. Discuss how many baby dinosaurs there are. Discuss how to use the part-whole model to help. This question is open-ended for the children to explore.
Five possible answers: 74 – 23 = 51; 75 – 23 = 52; 76 – 23 = 53; 77 – 23 = 54; 78 – 23 = 55
3. Help Cleo and Blake to work out how many more boulders they need to move to free the baby dinosaur.
Discuss how many boulders there are to begin with. Discuss how many have been moved so far. Discuss how to use column subtraction to work out the answer.
45 – 22 = 23 boulders left to move
4. Help Cleo and Blake to work out how many dinosaurs are left eating berries.
Discuss how many dinosaurs are in the herd. Discuss how many have moved away. Discuss which method we could use to work out the calculation presented in linear format.
95 – 42 = 53 dinosaurs are left eating berries.
Optional discussion points:
Discuss how these subtraction calculations could be checked.
National Curriculum Objectives
Mathematics Year 2: (2C4) Solve problems with addition and subtraction using concrete objects and pictorial representations, including those involving numbers, quantities and measures applying their increasing knowledge of mental and written methods
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