the average of 20 numbers is 0. of them, at the most, how many be greater than zero?
Here average of 20 numbers= 0.
So we have avg = sum/20.
That implies sum = 0.
Now for the sum of 20 numbers to be equal to zero, there may be all 19 numbers of them >0 and only one number which is -ve of all the 19 numbers sum.
So the answer is 19.