Current Situation:
18 boxes; 950 pebbles => ~52.7 pebbles/box (Mean)
Now, 2 more boxes are added and the questions is
Quote:
Is the average (arithmetic mean) number of pebbles per container for all 20 boxes greater than 52?
For mean to be greater than 52, the total pebbles in all boxes combined has to be >1040 (20*52). So, >90 pebbles would have to be added in the 2 extra boxes (1040 - 950). With that, lets see the statements:
St 1: (1) Each of the extra box added to the container has more than 30 pebbles.
This could be anything. If its 31 and 32 pebbles, for example, then the mean wouldn't go over 52. But if it is 60 and 61 pebbles, for example, then the mean would go over 52. So St 1 alone is not sufficient.
St 2: (2) Each of the extra box added to the container has less than 45 pebbles.
Now, for there to be >90 pebbles overall between the 2 extra added boxes, atleast one box needs to have >= 45 pebbles. Since both have lesser than 45 pebbles, the mean will not be >52.
So, St 2 alone is sufficient. Hence, B.