Alamp uses 28.5 amps of current and has a resistance of 12.8 ohms. how much power does it use?
a.365 watts
b.4670 watts
c.63.5 watts
d.10,400 watts

One of the formulas for electrical power is

         Power = (current²) x (resistance) .

This is a very handy formula to use right now. because this question TELLS us the current and the resistance, and it wants us to find the power.  Let's go:

         Power = (current²) x (resistance) .

                   = (28.5 A)² x (12.8 ohms)

                   =  10,396.8 watts .

Choice-D is apparently the one to pick.

This is a serious lamp ... one you don't want to mess with.
A typical incandescent lamp is maybe 20% efficient ...
20% of the power it uses gets turned into light, and the
other 80% gets turned into heat.  If that's true of the lamp
in this question, then when it's turned on ...

-- it shines with about 2,080 watts of light;

-- it oozes about 8,320 watts of heat into the room ... about
the same as five or six toasters, or seven blow-dryers, all
running full-blast. 
 

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.