The mean of 20 numbers is zero. Of them, at the most, how many may be greater than zero?
It’s given that mean of 20 numbers is 0, which implies that average of 20 numbers is 0.
This means that Sum of 20 numbers is 0.
If Sum of 19 numbers out of 20 is x(say), then the 20th number will be absolutely 0 for the average to be 0.
⇒ At the most, 19 numbers will be positive.