2021年4月概率论与数理统计（经管类）试题）
卷面总分：100分
试卷年份：2021.04
是否有答案：有
作答时间： 120分钟
设二维随机变量(X，Y)服从平面区域D={(x.y)|0≤x≤20≤y≤3}上的均匀分布，则E(XY)=
Fatal error: Uncaught Error: Call to a member function fetch_array() on boolean in /www/wwwroot/www.shzkw.org/phpcms/libs/classes/db_mysqli.class.php:153
Stack trace:
#0 /www/wwwroot/www.shzkw.org/phpcms/model/get_model.class.php(30): db_mysqli->fetch_next()
#1 /www/wwwroot/www.shzkw.org/caches/caches_template/default/content/yzb_exam_detail.php(153): get_model->fetch_next()
#2 /www/wwwroot/www.shzkw.org/phpcms/modules/yzb/exam.php(291): include('/www/wwwroot/ww...')
#3 /www/wwwroot/www.shzkw.org/phpcms/libs/classes/application.class.php(31): exam->detail()
#4 /www/wwwroot/www.shzkw.org/phpcms/libs/classes/application.class.php(19): application->init()
#5 /www/wwwroot/www.shzkw.org/phpcms/base.php(134): application->__construct()
#6 /www/wwwroot/www.shzkw.org/phpcms/base.php(85): pc_base::_load_class('application', 'libs/classes', 1)
#7 /www/wwwroot/www.shzkw.org/phpcms/base.php(76): pc_base::load_sys_class('application')
#8 /www/wwwroot/www.shzkw.org/index.php(15): pc_base::creat_app()
#9 {main}
thrown in /www/wwwroot/www.shzkw.org/phpcms/libs/classes/db_mysqli.class.php on line 153
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