Answer:
1st, 2nd, and 4th
Explanation:
1st conserves gasoline/petroleum
2nd conserves electricity
4th conserves paper
To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. Mathematically it can be described as,

Here,
= Frequency of Source
= Speed of sound
f = Frequency heard before slowing down
f' = Frequency heard after slowing down
v = Speed of the train before slowing down
So if the speed of the train after slowing down will be v/2, we can do a system equation of 2x2 at the two moments, then,
The first equation is,



Now the second expression will be,



Dividing the two expression we have,

Solving for v, we have,

Therefore the speed of the train before and after slowing down is 22.12m/s
The power dissipated across a component can be calculated through the formula P=I^2xR
Substituting the values in we get P=(0.5)^2x10=2.5W
The word "Per" means divide
"miles per gallon" is the same as "miles / gallon"
The truck went 1,200 miles
on 55 gallons
1,200 ÷ 55 = 21.81