The roman empire began in 27 b. c. and ended in 476 a. d. the persian empire lasted approximately 5/11 as long as the roman empire. based on this approximation, if the persian empire began in 550 bc, in what year did it end? round all years to the nearest whole number.

Step One
How many years did the Roman Empire Last?
Abs(27) + 476 = Roman Empire.
27 + 476 = 503 years.

Note the total number of years starts in BC. To add that to the AD number of years you have to take the absolute value of the 27. Otherwise you would be subtracting and that would make the total number of  years wrong by 54 years.

Step Two
Find 5/11 of the total number of years.
(5/11) * 503 = 228.6363 Hold off on rounding.

Step Three
Find the ending date.
Starting date = 550 BC
Ending date = ???
Number of years between Start and end = 228.6363
Ending date = starting date - 228.6363 you are working towards AD
Ending date = 550 - 228.6363
Ending date = 321.4 BC
Rounded that comes to 321 BC.