Amachine worked for 5 hours and used 4 kilowatts of electricity. the machine a kilowatt each hour it worked

The question is meaningless.  It uses "kilowatt" completely incorrectly.

"Watt" and "kilowatt" are rates at which energy is used, NOT
amounts of energy.

The question is a lot like saying that a car traveled for 5 hours at
4 miles per hour, so how many miles per hour did it travel each
hour it drove ?



If a machine used energy at the rate of 4 kilowatts when it's
running, then it uses 4 kilowatt-hours of energy during every
hour that it runs.
 
If it runs for 5 hours, then it uses

             (4 kilowatts x 5 hours) = 20 kilowatt-hours

of energy during that time.