Trains arrive at Pascal Station every $x$ minutes, where $x$ is a positive integer. Trains arrive at Pascal Station at many different times, including at 10:10 a.m., 10:55 a.m., and 11:58 a.m. Which of the following is a possible value of $x$ ?
(A) 9
(B) 7
(C) 10
(D) 5
(E) 11
The length of time between 10:10 a.m. and 10:55 a.m. is 45 minutes.

The length of time between 10:55 a.m. and 11:58 a.m. is 1 hour and 3 minutes, or 63 minutes. Since trains arrive at each of these times and we are told that trains arrive every $x$ minutes, then both 45 and 63 must be multiples of $x$. (In other words, if we count forward repeatedly by $x$ minutes starting at 10:10 a.m., we will eventually count 10:55 a.m. and then eventually count 11:58 a.m.)

Of the given choices $(9,7,5,10,11)$, only 9 is a factor of each of 45 and 63 .

ANSWER: (A)