Postman Stories for Multiplying Integers

1. Postman Stories for Multiplying Integers

2. What do you think? • Should a check be represented by a positive number, or a negative one?

3. What do you think? • Should a check be represented by a positive number, or a negative one? • Should a bill be represented by a positive number, or a negative one?

4. Remember . . . • Checks are positive numbers. • A check for $3 may be written as 3. • Bills are negative numbers. • A bill for $7 may be written as -7.

5. What do you think? • If the postman brings you mail, do you have more mail than before, or less? • Should this be a positive number, or a negative one? • If the postman takes away mail, do you have more mail than before, or less? • Should this be a positive number, or a negative one?

6. Remember . . . • If the postman brings you mail, it is represented by a positivenumber. • If he brings you 6 pieces of mail, write 6. • If the postman takes away mail, it is represented by a negative number. • If he takes away 10 pieces of mail, write -10.

7. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number?

8. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number? • Suppose each piece of mail was a check for $10. How would you write this number?

9. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number? • Suppose each piece of mail was a check for $10. How would you write this number? • What multiplication problem represents this situation?

10. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number? • Suppose each piece of mail was a check for $10. How would you write this number? • What multiplication problem represents this situation? 5x10 = ?

11. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number? • Suppose each piece of mail was a check for $10. How would you write this number? • What multiplication problem represents this situation? 5x10 = 50

12. Check It! 5x10 = 50 • Does the answer +50 make sense? Did you gain $50 when he brought you 5 checks for $10 each?

13. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number? • Suppose each piece of mail was a bill for $10. How would you write this number?

14. Let’s practice! • Suppose the postman brings you 5 pieces of mail. How would you write this number? • Suppose each piece of mail was a bill for $10. How would you write this number? • What multiplication problem is this? • What’s the answer to that multiplication problem?

15. Let’s Practice! • The postman brought you 5 pieces of mail. • Each piece of mail was a bill for $10. 5X-10 = -50

16. Does it make sense? • The postman brings you 5 pieces of mail. • Each piece of mail is a bill for $10. • You lost $50. This is the number -50! • Equation: 5X-10 = -50 • You lost $50. This is the number -50!

17. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10. • How can we express this mathematically?

18. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10. • How can we express this mathematically? (Write an expression!)

19. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10. • How can we express this mathematically? (Write an expression!) -5X10 = ?

20. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10. • Solution: -5X10 = -50

21. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10.

22. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10. • Write a math problem for this situation and solve it.

23. Let’s Practice • When you paid your bills, the postman took away 5 pieces of mail. • Each piece of mail was a check for $10. -5 x10 = -50

24. Does it make sense? • The postman took away 5 pieces of mail. • Each piece of mail was a check for $10. • Equation: 5X-10 = -50 • You have $50 less than before. This is the answer: -50!

25. Last Practice • It’s time to bill your customers for your business! • The postman takes away 5 pieces of mail. • Each piece of mail is a bill for $10.

26. Last Practice • It’s time to bill your customers for your business! • The postman takes away 5 pieces of mail. • Each piece of mail is a bill for $10. • Write an equation for this.

27. Last Practice • The postman takes away 5 pieces of mail. • Each piece of mail is a bill for $10. • Equation: -5X-10 = 50

28. Does It Make Sense? • The postman takes away 5 pieces of mail. • Each piece of mail is a bill for $10. • Equation: -5X-10 = 50 You made $50! That’s why the answer is +50.

29. Thanks to the original author of this power point. For corrections or improvements to this power point, please email teachmetime@gmail.com.