The water in the human body accounts for about (6/10) to (7/10) of the body weight, and Wenwen weighs 45 kilograms. In the answers below, how many kilograms represent the approximate mass of water in Wenwen's body.
人体中的水份约占人体体重的(6/10)～(7/10)，文文重45千克，下面的答案中，多少千克表示的是文文体内水份的大约质量．
<result>30</result>