quangviet512 wrote:

Tom is going to move, he has three kinds of boxes: large, medium, and small. Now he has already 11 large boxes, each of which is either empty or filled with 6 medium boxes. Medium boxes are filled in the large boxes and each of them is either empty or filled with 6 small boxes. Small boxes are empty and filled in the medium boxes. How many boxes does Tom have?

1). he has 56 empty boxes

2). he has 42 small boxes

I pick A

11 Large

say x filled , then 11 -x empty

=> 6x Medium boxes

say y filled, then 6x-y empty

=> 6y Small boxes

so we need to find, 11 + 6(x+y) ...

now 1 says

(11 -x) + (6x-y) + 6y = 56

=> 5x + 5y = 45

=> x + y = 9

so we can find 11 + 6(x+y) - hence sufficient

2 says

6y= 42

nothing about x hence insufficient.