the population of district a is three times the average population of the other nine districts in the city. what percent of the city's population lives in district a? any idea?
Let the average of the other nine cities be x, then the population of the nine districts is 9x. The total population of the city is a + 9x. But a = 3x. Hence, the total population is 3x + 9x = 12x. Therefore, the percent of the city's population living in district a is 3x/12x * 100 = 25%
