Math Investigations

Help with Opening PDF Files

Chapter 3

Part 1: Home and School Investigation

Send the Letter to Family (PDF file) home with each child. Once all of the children have brought in a picture of a subtraction situation they saw in a book or on television, have them share their pictures. After all the pictures are presented, write the subtraction sentence on the picture if that has not already been done. Display the pictures in the classroom and/or make a book of the pictures.

Part 2: Be an Investigator

A good time to do this investigation is after Lesson 2 on modeling subtraction.


  • jar
  • six counters

Introducing the Investigation

Introduce the investigation by putting six counters into a jar. Announce that you will take one of the counters out of the jar each day. Ask when the children think there will be zero counters in the jar? You will need to decide if you will take a counter out of the jar for Saturday, Sunday, or any other day the children do not come to school. Let the children know if you will do this or not. Make a chart that shows the prediction of each child. Allow space so that the predictions of the children can be revised as you do the activity. Then choose a volunteer to take a counter out of the jar.

Doing the Investigation

Each day ask the children if they would like to change their predictions. Make any changes on the chart. Then choose a volunteer to take a counter out of the jar. Also, take a counter out of the jar for any non-school days if you have decided to take counters out of the jar for those days too. As you get closer to no counters in the jar many of the children will revise their earlier prediction to a more accurate one.

Extending the Investigation

Repeat the activity with a different number of counters in the jar.

Houghton Mifflin Math Grade 1