Question

You pick two digits at random without replacement and write them in the order picked what is the probability that you have written the first two digits of your phone number assume there no repeats of digits in your phone number

Answer 1

1/90.

Explanation:

There are 10 digits 0 to 9 .

I am assuming that your phone number can begin with a 0.

Prob(you get the first digit right) = 1/10

Prob(you get the second one right) = 1/9

* ( as there are only 9 to pick from after the first pick.

The answer is 1/10 * 1/9 = 1/90.