Atrain travels 72 kilometers in 1 hours, and then 64 kilometers in 1 hours. what is its average speed?

To find the average of something you must first add everything together and then divide it by the total amount of numbers you added together.

First add 72 and 64 together

72+64=136

Now divide 136 by 2

136/2=68

So the average speed of the train is 68 kilometers

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia