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        Mathemateg

         

        ACE - Subtraction

        Let's do a quick warm-up activity! 
        I wonder, can you spot the odd one out?
        Talk to your partner.
        What strategies have we been exploring?
        Talk to your partner. Let's activate our prior knowledge.

         

        Let's solve an ACE question together!
        Remember we need to Analyse,  Create, and Evaluate.
         
        180 pupils are competing in sprint races. Each pupil needs: 
        • 3 bibs 
        • 2 pencils 
        12 adults are helping. Each adult needs: 
        • 1 pencil 
        • 2 bibs 
        Tasks: 
        1. Calculate total number of items.
        • How many bibs are needed altogether? 
        • How many pencils are needed altogether?
        1. If only 370 bibs are available, how many more are needed? 
        2. If 27 pencils are broken, how many pencils are still usable?
        3. How did you check your totals? 
        4. Can you represent your answers in a different way (e.g., bar model or a part–whole diagram)?

         

        Analyse
        Step 1:
        Total number for pupils
        • Bibs: 180 x 3 = 540 
        • Pencils: 180 x 2 = 360
        Step 2:
        Total number for adults
        • Pencils: 12 x 1 = 12 
        • Bibs: 12 x 2 = 24 
        Step 3:
        Grand total 
        • Bibs: 540 + 24 = 564 
        • Pencils: 360 + 12 = 372 
        Step 4:
        Subtractions 
        • Bibs: 564 – 370 = 194 
        • Pencils: 372 – 27 = 345
         
        Create 
        You could create a table or diagram to show your findings and help you organise your workings: 
        Items 
        Totals 
        Bibs 
        564 
        Pencils 
        372 
         
        Evaluate 
        1. How did you check your totals? 
        • I used the inverse operation to check my answers. 
        1. Can you represent your answers in a different way (e.g., bar model, part–whole diagram, or subtraction sentences)? 
        • I can represent my totals by showing a bar model.
         
        Now you can try your own ACE questions. Remember to show your workings and explain your thinking! Use the sentence starters to help you explain your answers.

        • “I know the total of____ is ____ because” 

        • “I added ___ and ___ because…” 

        • “My number sentence is…” 

        • “I used bar models to show…” 

        • “This helped me see…” 

        • “I chose this method because…” 

        • “This representation shows that…” 

        • “I know this is correct because…” 

        • “I noticed that…” 

        • “I organised my workings by…” 

        • “I used a diagram to help me because…” 

        • “I partitioned each number into...” 

        • “I checked my answer using the___method.”

        • “Another way to solve this is…” 

        • “This method is quicker because…” 

        • “I prefer this strategy because…” 

        • “Using the___method helped me check my answer.” 

        • “I had to carry/exchange when I added/subtracted...” 

        • “I can prove my answer is correct because…” 

        Reflection 

        • “I preferred using…” 

        • “Next time I will…” 

        • “I learnt that…” 

        • “I found ___ challenging because…” 

         

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