Answer: 1 Kilogram.
Explanation:
 You  know that the weight of one box is 
 kilograms.
 kilograms.
 You also know that Micheal has 
 boxes.
 boxes.
 If you want to know the total weight of Micheal's boxes when empty, you need to multiply the weight of one box by the total number of boxes that Micheal has.
 You need to remember the Product of powers property:
 

 Then:
 

 Remember that: 
 

 Then, the result is:
 
