Answer:
 the mass of the air in the classroom = 2322 kg
Explanation:
given:
A classroom is about 3 meters high, 20 meters wide and 30 meters long.
 If the density of air is 1.29 kg/m3
find:
 what is the mass of the air in the classroom?
density = mass / volume
where mass (m) = 1.29 kg/m³
volume = 3m x 20m x 30m = 1800 m³
plugin values into the formula
   1.29 kg/m³   =  <u>      mass    </u>
                              1800 m³
mass =  1.29 kg/m³  ( 1800 m³ )
mass = 2322 kg
therefore,
 the mass of the air in the classroom = 2322 kg
 
        
                    
             
        
        
        
The correct answer should be <span>A. If you see a wear bar across the width of the tread, it's time to change the tire
This is an incorrect sentence because you should change a tire before you see the wear bar. At the time you see the bar, you should've already changed it. </span>
        
             
        
        
        
I = E / R
If the resistors are in series, the current is 0.3 Amperes.
If the resistors are in parallel, the current is 1.25 Amperes.
        
             
        
        
        
I think it would be the scientific method.