Предмет: Математика, автор: se23rg

в группе студентов из 20 человек 12 юношей и 8 девушек. Для дежурства случайным образом отобраны 2 студента. Какова вероятность того, что среди них будет 1 юноша и 1 девушка

Ответы

Автор ответа: sedinalana

Всего вариантов С(2,20)
Вариантов выбора девушки С(1,8)
Вариант выбора юноши С(1,12)
С(1,8)*С(1,12)/С(2,20)=
=8!*12!*2!*18!/(7!*11!*20!)=
=7!*8*11!*12*1*2*18!/(7!*11!*18!*19*20)=48/95≈0,505

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