Multiplication Strategies and Relationships

The video tutorial introduces various multiplication shortcuts and strategies to simplify calculations. It covers doubling techniques for multiplying by 2, 4, and 8, and explains how to multiply by 10 and 100 by adding zeros. The tutorial also explores methods for multiplying by 5 and 9, highlighting the relationships between these numbers and 10. The teacher emphasizes understanding the logic behind these shortcuts to enhance mathematical efficiency.

What is the strategy for multiplying a number by 4?

• Add the number four times

• Subtract 2 from the number

• Double the number twice

• Multiply by 2 and then add 2

How can you quickly multiply a number by 10?

• Add 10 to the number

• Multiply the number by 2 and then by 5

• Subtract 10 from the number

• Add a zero to the end of the number

What is the relationship between 5 and 10 that helps in multiplication?

• 5 is 10 minus 5

• 5 is double of 10

• 5 is half of 10

• 5 is 10 plus 5

How do you multiply a number by 5 using the relationship with 10?

• Double the number and add 5

• Halve the number and multiply by 10

• Add 5 to the number and multiply by 2

• Subtract 5 from the number and multiply by 10

What is the first step in the strategy for multiplying by 9?

• Multiply by 8

• Multiply by 10

• Add 9

• Subtract 1

After multiplying by 10, what is the next step to multiply by 9?

• Divide by 2

• Multiply by 2

• Subtract the original number

• Add the original number

Why does the strategy of multiplying by 9 work?

• Because 9 is double of 4.5

• Because 9 is one less than 10

• Because 9 is one more than 8

• Because 9 is half of 18

What is an alternative strategy for multiplying by 9?

• Find a pair of digits that add up to 10

• Find a pair of digits that add up to 9

• Find a pair of digits that add up to 8

• Find a pair of digits that add up to 7

If you are multiplying 8 by 9 using the alternative strategy, what is the first step?

• Subtract 9 from the number

• Go back one number

• Go forward one number

• Add 9 to the number

What is the result of multiplying 7 by 9 using the alternative strategy?

• 81

• 72

• 54

• 63