5: Early Additive - Addition and Subtraction

 

Erin takes 37 minutes to run the cross country. Brian takes 9 minutes more than Erin. How long does Brian take?


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Student: Thirty-seven plus three equals forty. Forty plus six equals forty-six.
Teacher: Could you work it out a different way?
Student: Thirty-seven plus ten would be forty-seven, but that is one too many so the answer is forty-six.

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At the Early Additive stage, students have begun to recognise that numbers are abstract units that can be treated simultaneously as wholes or can be partitioned and recombined. This is called part-whole thinking.