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Present Postage

6NS3

Adapted from Problem Driven Math Grade 6

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Bridget has a roll of 34¢ stamps and another roll of 21¢ stamps. She wants to mail a package that needs $2.54 in postage.

What do you notice?

What do you wonder?

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Bridget has a roll of 34¢ stamps and another roll of 21¢ stamps. She wants to mail a package that needs $2.54 in postage.

How might Bridget use the stamps she has to get exactly $2.54 in postage?

How might you get started?

How could you organize your work?

Turn and Talk

Questions to ask:

How can you organize your work?
Why can’t Bridget use only 34 cent stamps?
Why can’t she use only the 21 cent stamps?
What is the greatest number of 34 cent stamps she can use? How do you know? What is the value of this?
If she uses 5 of the 34 cent stamps, how many 21 cent stamps would she use?

What to look for: If students are creating a list for guess and check, have them keep an organized chart so that they can use their guesses to determine a final answer. The standard algorithm for addition and subtraction of decimals must be grounded in understanding. We are not simply lining up the decimal points, we are aligning every place value. Ensure that students who are adding/subtracting/multiplying decimals are placing the decimal point in the correct place and ensuring that their answers are reasonable. Look for students who can recognize that reasoning about multiples can help you determine an answer.

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Bridget has a roll of 34¢ stamps and another roll of 21¢ stamps. She wants to mail a package that needs $2.54 in postage.

How can Bridget use the stamps she has to get exactly $2.54 in postage?

Solve the problem

Consider having students works in pairs to solve this problem.

Questions to ask:

How can you organize your work?
Why can’t Bridget use only 34 cent stamps?
Why can’t she use only the 21 cent stamps?
What is the greatest number of 34 cent stamps she can use? How do you know? What is the value of this?
If she uses 5 of the 34 cent stamps, how many 21 cent stamps would she use?

What to look for: If students are creating a list for guess and check, have them keep an organized chart so that they can use their guesses to determine a final answer. The standard algorithm for addition and subtraction of decimals must be grounded in understanding. We are not simply lining up the decimal points, we are aligning every place value. Ensure that students who are adding/subtracting/multiplying decimals are placing the decimal point in the correct place and ensuring that their answers are reasonable. Look for students who can recognize that reasoning about multiples can help you determine an answer.

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Bridget has a roll of 34¢ stamps and another roll of 21¢ stamps. She wants to mail a package that needs $2.54 in postage.

How can Bridget use the stamps she has to get exactly $2.54 in postage?

Debrief the problem

Let’s share!

What strategy did you use?

How did you organize your work?

Consider having students works in pairs to solve this problem.

Questions to ask:

How can you organize your work?
Why can’t Bridget use only 34 cent stamps?
Why can’t she use only the 21 cent stamps?
What is the greatest number of 34 cent stamps she can use? How do you know? What is the value of this?
If she uses 5 of the 34 cent stamps, how many 21 cent stamps would she use?

What to look for: If students are creating a list for guess and check, have them keep an organized chart so that they can use their guesses to determine a final answer. The standard algorithm for addition and subtraction of decimals must be grounded in understanding. We are not simply lining up the decimal points, we are aligning every place value. Ensure that students who are adding/subtracting/multiplying decimals are placing the decimal point in the correct place and ensuring that their answers are reasonable. Look for students who can recognize that reasoning about multiples can help you determine an answer.

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Debrief the problem - Deja’s method

Bridget has a roll of 34¢ stamps and another roll of 21¢ stamps. She wants to mail a package that needs $2.54 in postage. How can Bridget use the stamps she has to get exactly $2.54 in postage?

34¢ Stamp Quantity	Total Value 34¢ stamps	21¢ Stamp Quantity	Total Value 21¢ stamps	Overall Total
3	$1.02	3	$0.63	$1.65
5	$1.70	5	$1.05	$2.75
5	$1.70	4	$0.84	$2.54

How was Deja’s strategy similar or different than yours?

Questions to ask:

What strategy did you use to determine your answer? Did you calculate the same solution?
How did I solve the problem?
What number of 21 cent stamps should be used?

Mathematics ideas to highlight: What to look for: If students are creating a list for guess and check, have them keep an organized chart so that they can use their guesses to determine a final answer. The standard algorithm for addition and subtraction of decimals must be grounded in understanding. We are not simply lining up the decimal points, we are aligning every place value. Ensure that students who are adding/subtracting/multiplying decimals are placing the decimal point in the correct place and ensuring that their answers are reasonable. Look for students who can recognize that reasoning about multiples can help you determine an answer.

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Extension

Peter went to the Post Office to purchase stamps. He bought one stamp each of the following values:

$0.49 $0.70 $1.15 $6.65

What was the total he was charged? (without tax)

If he paid for the stamps with a $20 bill, what was his change?

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Practice

$6.49 + $13.21 + $4.85 =

$21 -$3.85 =

$ 0.49 + $1.25 + 3.67=

$45 - $19.99 =

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Solve.

$6.49 + $13.21 + $4.85= ____________

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Solve.

$21 -$3.85 = _______________

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Solve.

$ 0.49 + $1.25 + 3.67 = ____________

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Solve.

$45 - $19.99 = ____________

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Present Postage

6NS3

Adapted from Problem Driven Math Grade 6

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Name______________________ Date ________________

Bridget has a roll of 34¢ stamps and another roll of 21¢ stamps. She wants to mail a package that needs $2.54 in postage.

How can Bridget use the stamps she has to get exactly $2.54 in postage?

Consider having students works in pairs to solve this problem.

Questions to ask:

How can you organize your work?
Why can’t Bridget use only 34 cent stamps?
Why can’t she use only the 21 cent stamps?
What is the greatest number of 34 cent stamps she can use? How do you know? What is the value of this?
If she uses 5 of the 34 cent stamps, how many 21 cent stamps would she use?

What to look for: If students are creating a list for guess and check, have them keep an organized chart so that they can use their guesses to determine a final answer. The standard algorithm for addition and subtraction of decimals must be grounded in understanding. We are not simply lining up the decimal points, we are aligning every place value. Ensure that students who are adding/subtracting/multiplying decimals are placing the decimal point in the correct place and ensuring that their answers are reasonable. Look for students who can recognize that reasoning about multiples can help you determine an answer.

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Peter went to the Post Office to purchase stamps. He bought one stamp each of the following values:

$0.49 $0.70 $1.15 $6.65

What was the total he was charged? (without tax)

If he paid for the stamps with a $20 bill, what was his change?