The weight of all 40 apples in the second box is : 144 x 40 = 5760 (g)
The total weight of all 90 apples in both boxes : 5760 + 6300 = 12060 (g)
To find the mean weight of an apple in the big container, we take the total weight of both boxes (12060) divided by the total amount of quantities (apples in both boxes)
So, the mean weight of an apple in the big container is 12060 : 90 = 134(g)