import java.util.Scanner; public class Main{ public static void main(String []args){ Scanner sc = new Scanner(System.in); int up = sc.nextInt(); int down = sc.nextInt(); int height = sc.nextInt(); double area = (up + down) * height * 0.5; System.out.printf("%.3f",area); } }这题需要掌握梯形的面积,因为梯形的边长都是整数型,面积是浮点型,乘个0.5使其变成浮点型,在输出结果就行了。