The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?

Question: The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?

Solution:
Average of 20 numbers = 0
Sum of 20 numbers = (0 × 20) = 0
It is quite possible that 19 of these numbers may be positive and if their sum is a, then 20th number is (- a).

Therefore, at the most 19 numbers can be greater than zero.