N is the number of shopping carts in the train.
length_cm is the total length of the train in centimeters.
notes is where we recorded a few unusual circumstances.

How long is one shopping cart?

How much does one shopping cart fit into the next one?

Do any of the notes seem to make a difference?

One set of carts was 486 cm long. How many carts?

(data by Susan English and Tim Erickson, 2004)