the population of snowtown was 4500 in 1990.In 1994,it had decreased to 3600.Find the percent decrea

题目

the population of snowtown was 4500 in 1990.In 1994,it had decreased to 3600.Find the percent decrease in population during those four years.如果有公式也一起给我,给个详解

答案

原意：1990年……的人口是4500人,在1994年则下降到3600.求下降率.
（4500－3600）/4500＝20％