Official Solution: If the average (arithmetic mean) of four positive integers is 30, how many of these four integers are greater than 20? The average of the four
positive integers is 30, which means that the sum of these four positive integers is \(4*30=120\).
(1) One of the integers is 98.
If one of the integers is 98, then the sum of the other three is \(120-98=22\). Since all the integers are positive, none of these three remaining integers can be greater than 20 (the largest possible value for one of them is 20, if the other two are both 1). Therefore, there is only one integer greater than 20, which is 98. Sufficient.
(2) The median of the four integers is less than 12.
If the set is \(\{1, 1, 1, 117 \}\), then there is only one integer greater than 20. However, if the set is \(\{1, 1, 21, 97 \}\), then there are two integers greater than 20. Not sufficient.
Answer: A