Hit and Run
A witness took a picture of a hit and run accident, and the middle 3 symbols are visible, as shown below, but the rest of the symbols are blurred.
The witness knows that a license plate has 3 digits and 3 uppercase alphabets in that order.
The police went through their database in hopes to identify the culprit. What is the average number of they need to search before they can find the actual culprit?
The answer is 1300.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
If we ignore the fact that the actual numbers in the blurred locations can be read and assume that they are invisible completely, say behind greenery, we have two digits, which can independently be any of 10 possibilities, and one letter, with 26 possibilities. That is 2600 searches, all of them equally likely to lead to the correct answer. So half of that would be the expected number.
2 2 6 0 0 = 1 3 0 0