Question

A California licence plate consists of a sequence of seven symbols: number, letter, letter, letter, number, number, number, where a letter is any one of 26 letters and a number is one among 0, 1, . . . , 9. Assume that all licence plates are equally likely. (a) What is the probability that all symbols are different

Answer 1

Answer:

There is a 44.73% probability that all symbols are different.

Step-by-step explanation:

A probability is the number of desired outcomes divided by the number of total outcomes.

There are 26 total letters and 10 total digits.

The plate has the following format:

number, letter, letter, letter, number, number, number

Total outcomes

Each number can have 10 values.

Each letter can have 26 values.

There are four numbers and 3 letters.

So there are

$10^{4}*26^{3} = 175760000$ possible plates

Desired outcomes

We cannot have repeated values.

So, for example, the first number can be any of the 10 digits. The second can be any of them, bar the first one. So 9 possible digits

The same logic for the letters, 26, then 25, then 24.

So there are

10*26*25*24*9*8*7 = 78624000 plates in which all symbols are different.

(a) What is the probability that all symbols are different

$P = \frac{78624000}{175760000} = 0.4473$

There is a 44.73% probability that all symbols are different.