Place a container of interlocking cubes, a small dry erase board, a dry erase marker and a train set with three or more cars in front of you on the rug at kindergarten circle time. Hold up a train car and one interlocking math cube. Tell the students that you want to measure the train car by finding out how many cubes you will need to make a row of cubes that is the same length as the train car.
Draw two lines on the dry erase board an equal distance apart to make three columns. Write the words "Name of train car" at the top of the first column, write the words "Cube number predicted" at the top of the second column, and write "Cubes actually used" at the top of the third column. Explain to the students that you will write the name of the train car (e.g. engine, coal car, box car) in the first column, how many cubes you predict will be needed to make a row of cubes that is the same length as the train car in the second column, and the actual amount of cubes used to make a row of cubes the same length as the train car in the third column.
Choose a train car and hold it up for all the students to see. Say the name of the car and write the name of the car in the first column on the dry erase board (e.g. passenger car). Estimate the number of interlocking math cubes you may need to to make a row of cubes the same length as the train car, say the number and write it in the second column (e.g. 25 cubes). Connect the number of cubes you estimated together and place them next to your train car on the rug. Remove any cubes necessary if your estimate was too high or add necessary cubes if the estimate was too low. Write the amount of cubes it actually took to make a row that was the same length as the train car in the third column and review your column entries with the students.
Invite students to come up and continue the process by measuring the length of rest of the train cars with the interlocking cubes.