Transcript mailing-multiplication-presentation[1]

Postman Stories for
Multiplying Integers
What do you think?
• Should a check be represented by a
positive number, or a negative one?
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?
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.
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?
Remember . . .
• If the postman brings you mail,
it is represented by a positive
number.
– 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.
Let’s practice!
• Suppose the postman brings you 5 pieces
of mail. How would you write this number?
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?
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?
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?
5 x 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?
5 x 10 = 50
Check It!
5 x 10 = 50
• Does the answer +50 make sense? Did
you gain $50 when he brought you 5
checks for $10 each?
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?
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?
Let’s Practice!
• The postman brought you 5 pieces of mail.
• Each piece of mail was a bill for $10.
5 X -10 = -50
Does it make sense?
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•
•
•
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:
5 X -10 = -50
• You lost $50. This is the number -50!
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?
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!)
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!)
-5 X 10 = ?
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:
-5 X 10 = -50
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.
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.
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 x 10 = -50
Does it make sense?
• The postman took away 5 pieces of mail.
• Each piece of mail was a check for $10.
• Equation:
5 X -10 = -50
• You have $50 less than before. This is the
answer: -50!
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.
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.
Last Practice
• The postman takes away 5 pieces of mail.
• Each piece of mail is a bill for $10.
• Equation:
-5 X -10 = 50
Does It Make Sense?
• The postman takes away 5 pieces of mail.
• Each piece of mail is a bill for $10.
• Equation:
-5 X -10 = 50
You made $50!
That’s why the answer is +50.
Thanks to the original author of this power point.
For corrections or improvements to this power point, please email [email protected].