Frank Portman shows how to figure out how many taxicabs—or tanks—there are:
For the uninitiated, the Taxicab / Germany Tank problem is as follows:
Viewing a city from the train, you see a taxi numbered x. Assuming taxicabs are consecutively numbered, how many taxicabs are in the city?
This was also applied to counting German tanks in World War II to know when/if to attack. Statstical methods ended up being accurate within a few tanks (on a scale of 200-300) while “intelligence” (unintelligence) operations overestimated numbers about 6-7x. Read the full details on Wikipedia here (and donate while you’re over there).
Click through for the solution and how to implement it in R.