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Post-Office Numbers

  • Lesson
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Number and Operations
Location: Unknown

A post office is a good example of a real-world environment in which numbers of different types can be found. Whole numbers and fractions are introduced. Numbers that occur in a greater variety of measurement situations can also be introduced. At this level, students should be encouraged to elaborate on the way numbers are used.

Ask students to discuss the types of things they might see at a post office. Brainstorm a class list on the chalkboard or overhead. For example, students might mention:

  • Signs with postal rates (prices for stamps, Priority Mail, extra services, etc.)
  • Mailing supplies (boxes, envelopes, padded envelopes, tubes, etc.)
  • Stamps for collectors
  • Forms for different types of mailing (certified mail, registered mail, etc.)
886 post office

Students should visit the website of the United States Postal Service (perform a simple internet search to find this). Give them time to explore the site. Using the list of items brainstormed at the start of the lesson, have students locate information on some of those items (for example, postal rates). Students should complete the following activities.

Students could determine the cost of mailing 1,000 postcards. Students should locate the cost of mailing a postcard and use that to determine the total amount. Students may need to consider the following before proceeding:

  • postcards mailed within the United States will have a different postal rate than postcards mailed outside the United States
  • postcards have certain minimum and maximum size requirements (particularly width and length)

Similarly, students could determine the cost of mailing 1,000 letters. (Once again, you may need to discuss destination, i.e. U.S. and International, as well as size requirements.) As a class, discuss the advantages to bulk rate mailings and what this means.

Challenge the students to tell how numbers could be used to:

  • describe the size of a group of pieces of mail in a bulk mailing:
    numbers less than 100
    between 100 and 1,000
    between 1,000 and 10000
    or greater than 10000
  • identify locations--ZIP codes, street numbers on addresses
  • represent fractions, particularly on mailing requirements (namely length and width of letters and packages)
  • express measurements--weight, time for mailing, money (cost of postage), and so on


Calvin Irons and Rosemary Irons. "IDEAS: Numbers and Language." The Arithmetic Teacher. January, 1993, 40, 5. p 264 - 77.
  • Computers and Internet Connection
  • Information from the United States Postal Service 


  1. Ask the students how numbers are used to describe length at the post office. They could visit or write the post office to find out the restrictions on the length of packages. They should then visualize the size of a package that might fit the restrictions.
  2. Discuss the number 1,000. Ask the students to give different ways to describe it or think of it.

    For example,

    • "About one thousand girls and boys attend our school" or
    • "I take more than one thousand steps to walk around the edge of the playground."

    Have the students work in pairs to make up real-world questions about the post office. The answer to each question must be 1,000.

888 swim
Number and Operations

Sports Numbers

Students are familiar with sports and sporting events. Whole numbers and fractions are used to represent the size of groups or collections and measurements involving lengths, weights, and times in many sporting and game situations. This knowledge can be used to give the students another picture of numbers.

Learning Objectives

Students will:

  • Discuss, describe, read, and write about whole numbers to thousands, decimals to hundredths, and common fractions.
  • Identify various uses of numbers at the Post Office.

NCTM Standards and Expectations

  • Understand the place-value structure of the base-ten number system and be able to represent and compare whole numbers and decimals.
  • Recognize equivalent representations for the same number and generate them by decomposing and composing numbers.

Common Core State Standards – Mathematics

Grade 3, Num & Ops Fractions

  • CCSS.Math.Content.3.NF.A.1
    Understand a fraction 1/b as the quantity formed by 1 part when a whole is partitioned into b equal parts; understand a fraction a/b as the quantity formed by a parts of size 1/b.

Grade 4, Num & Ops Base Ten

  • CCSS.Math.Content.4.NBT.A.2
    Read and write multi-digit whole numbers using base-ten numerals, number names, and expanded form. Compare two multi-digit numbers based on meanings of the digits in each place, using >, =, and <. symbols to record the results of comparisons.

Grade 5, Num & Ops Fractions

  • CCSS.Math.Content.5.NF.B.3
    Interpret a fraction as division of the numerator by the denominator (a/b = a ÷ b). Solve word problems involving division of whole numbers leading to answers in the form of fractions or mixed numbers, e.g., by using visual fraction models or equations to represent the problem. For example, interpret 3/4 as the result of dividing 3 by 4, noting that 3/4 multiplied by 4 equals 3, and that when 3 wholes are shared equally among 4 people each person has a share of size 3/4. If 9 people want to share a 50-pound sack of rice equally by weight, how many pounds of rice should each person get? Between what two whole numbers does your answer lie?