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Teacher Feature

Location, location, location!


This hands-on activity teaches students about probability using coins as manipulatives.  Students will also explore the factors that affect probability.


Note:  For this activity, each group will need a bag with 10 coins (of varying denominations) inside it and a United States map.

Have students visit Fun Fact Number 43, or write the following on the board:

How can you tell where a coin came from?  Mint marks show what minting facility your coins came from—"P" for Philadelphia, "D" for Denver, and "S" for San Francisco.  This mark can be found to the right of the subject's face on the obverse side of each circulating coin-with the exception of the "Philadelphia" Lincoln cent, which has no mint mark.

Separate the class into groups of 2-3 students.  Each group should receive one bag with 10 coins inside, the "It's In The Bag!" handout, and a copy of a United States map.

Students will be looking for the letters D, S, or P on each coin.  Remind them that, depending on the coin, the marking may be on the obverse or the reverse of the coin.  Be sure that students mark one tally for each coin in their bag.  When they are finished, have them check their work by verifying that they have 10 tallies on their chart.

In the second row of the chart, have students calculate the fraction of total coins that were from Denver, San Francisco, and Philadelphia, respectively.  This result should be written in fraction form in each box.

Once the students have completed this, review with them the process of finding a percentage.  Remind them that all they need to do is divide the denominator by the numerator in the fractions in the second row of the chart.  Students can calculate the percentages and record them in the third row on the chart.

When the groups have completed their charts, they may begin using the map and answering the group questions.  Students may need help making the connection that it is more probable for older coins from the furthest Mint to have circulated to their state than younger coins (Or that younger coins will have most likely originated in a Mint closer to home.)

Question Seven can spark a class discussion on other contributing factors of probability.  What else could affect the probability of this coin exercise?  (number of coins released that particular year from each Mint, particular coins struck at specific Mints, etc.)


Using the same bag of coins, students can examine other probabilities and their contributing factors, such as:

  1. Are you more or less likely to have coins that are less than 20 years old?
  2. Are you more or less likely to have coins that display a portrait of a person with a ponytail on the obverse?
  3. Are you more or less likely to see a plant or tree on the obverse of the coin?


The project described above reflects some of the national standards of learning as defined by the National Council for the Social Studies (NCSS), the National Council for Teachers of English (NCTE), and the International Society for Technology in Education.  These standards are listed below:

Mathematics Standards

Data Analysis and Probability:  Students will determine the probability of drawing coins from each of the three United States Mints.

Measurement:  Students will need to measure the distance between the Mints and approximate which one is closest to them.

Number and Operations:  will learn how to convert fractions to percentages.

Science Standards

Science as Inquiry:  Students use their skills of observation to examine the mint marks on coins, and gather appropriate data.

Social Studies Standards

People, Places, and Environment:  Students will practice map skills as they locate four US cities/states, and compare the distances between each location.

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