Unit 3 Contents

Irma's method:

Irma drew a rectangle to show a way to multiply 20 classrooms 30 students.

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That means there are about 600 students in our school.

Nila and Tanya thought of two more strategies to multiply 30 students 20 classrooms.

Nila's method:

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Tanya's method:

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Tanya rewrote 20 30 into smaller factors. Then she changed the order of two factors. Mathematicians call this the commutative property.

1. Explain how Tanya used the commutative property. How did she change the order of the factors?
2. Use Irma's rectangle method to estimate the product of 33 49.
3. Use any method to estimate the product of 71 58.
4. What strategy is most efficient: Irma's, Nila's, Tanya's, or a different strategy? Explain your thinking.