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By the next day, Nila and Irma had finished cutting out all the stars. Nila's dad helped them hang the stars from the ceiling tiles in their classroom after school. Just for fun they decided to calculate the number of ceiling tiles for the whole school building. They estimated that the entire ceiling of the building was about 200 tiles wide and 300 tiles long. They used Nila's method and Alexis's method.
- Find the following sets of products using any method you choose. Look for patterns as you solve the problems. Check your work on a calculator.
- Irma learned to look for patterns when multiplying numbers that end in zeros. What patterns do you see from the products you found in Question 10?
- Nila wants to multiply 40 40 in her head easily. What method do you think she should use? What is 40 40?
- Nila thought of a rule for multiplication. She said, “To multiply numbers that end in zero, you just multiply the numbers without the zeros on the ends, and then put as many more zeros on the end of the product as there are in the numbers.” Do you agree? If so, why do you think the rule works?
- Alexis says multiplying 60 500 is tricky. What is 60 500? Why is it tricky?