Aptitude - Average - Discussion

Thanks for explaining @Tarun.

It may be possible that all numbers are negative and only one is positive like
(-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1+19)/20 = 0.

Here, it is asked that at the most, how many may be greater than zero.
So let see.

(1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1-19)/20 = 0.
Now see it's 19 number which is greater 0.

The answer could be 10.

Here, it is asked that, how many numbers may be greater than 0 and not will be greater than 0! please explain the difference?

@Tarun.

Good explanation. Thank You.

The average of two numbers A and B is 20, that of B and C is 19 and of C and A it is 21. What is the value of A?

First when average can be Zero:
0(Sum of observation)/20 Number of Observations =0 is answer (Average).

Than means we must get 0 sum on the top of /20 that will make average Zero.

Even single nagative number can make 0 on top of /20. If sum of 19 numbers is +1 one nagative number -1 can make it zero you can assume sum of 19 numbers as positive and put same nagative number to make it Zero.


Now coming to answer, they are asking how many number can be above 0 i.e. in positive (numbers below zero are nagative). 19 Max number can be positive to make one nagative number 0 so that we get average zero.

Hope it's clear now.

If you consider 20 numbers for example like.
-10,-9,.....,-1,+1,+2,.....+10.

Then the no of numbers greater than 0 is 10.

If the question includes "at least ".

Then the answer is 1.