1/5 + 1/4 =1/x
4x + 5x = 20
9x = 20 
x = 2.22 hours  Answer
        
             
        
        
        
Answer:
Explanation:
Scientists know that there are 6x1023 molecules in a mole - so we have about 0.5x1023 molecules in our marble…and since every silicon dioxide molecule has one atom of silicon and two of oxygen, we have a grand total of 1.5x1023 atoms. That's 150,000,000,000,000,000,000,000 atoms
 
        
             
        
        
        
A flow of a electric charge.
        
             
        
        
        
Answer : Mass
Explanation : Mass measures the amount of matter in a substance or an object.