Average of 29 numbers is 0. How many maximum possible numbers of above 0?

28

For being the average of 29 numbers to be zero, it is necessary that the sum of all numbers should be zero. let the sum of 28 numbers is x, Now it is necessary that the 29th number should be -x. Max 28 numbers be greater than zero and 29th term will be opposite sign of sum of 28 terms.