7: Advanced Multiplicative - Addition and Subtraction

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There are 121 students at Sarah's school. Sixty-six of them are girls. How many are boys?

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Student: I know that one hundred and twenty-one is eleven times eleven, and sixty-six is six times eleven. Eleven times eleven minus six times eleven is five times eleven, so there are fifty-five boys.

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Students at the Advanced Multiplicative stage are learning to choose appropriately from a range of part-whole strategies to solve and estimate the answers to problems involving multiplication and division. These strategies require one or more of the numbers involved in a multiplication or division to be partitioned, manipulated, then recombined.