When forming a two-digit number from the set ,
determine the event in which the units digit is two times its tens
Since the event is forming a two-digit number from the set ,
where the units digit is two times the tens digit, the elements of
the set representing the event must include a multiple of 2 that
is either 1, 2, 3, 4, or 9 for the units digit. The multiples of 2
are 2 and 4, so these are the units digits. This means that the
tens digits are and .
Thus, the set represents the event.