math
posted by bob on .
I look at a random time of day at a digital clock (that shows times from 1:00 through 12:59). What is the probability that (ignoring the colon) I see a palindrome such as 8:08? Express your answer as a common fraction.

20

1/10000000000000000000000

y'all are soooooooooooooooooooooooooooooo stupid. Anonymous is right

iT IS 20

Actually, it isn't. It's a fraction answer. :)

I think it's 19/240

its 19/240

First, we compute the total number of possible times that can show. There are 12 possible hours, and 60 possible minutes, so the total number of possible times is 12*60 = 720.
Now we compute the number of palindromes. There are 6 palindromes per hour for the nine hours 1 through 9 (1:01, 1:11, 1:21, 1:31, 1:41, 1:51 for example). There is one palindrome per hour from 10 through 12, namely 10:01, 11:11, and 12:21. Hence, the number of palindromes is 6*9 + 3 = 57.
Therefore, the probability that the time is a palindrome is 57/720 = 19/240