Предмет: Алгебра, автор: Аноним

Сколькими способами из числа 30 учащихся класса можно выбрать культорга и казначея?

Ответы

Автор ответа: olgaua64
1

Відповідь:

870

Пояснення:

так как культорг и казначей разные должности, то есть значение кто из 2 выбранных кем будет, поэтому количество способов такого выбора будет

A(2, 30)=30!/(30-2)!=30!/28!=29×30=870

или

количество способов выбрать 2 человек с класса С(2, 30) умножаем на 2, так как каждый из выбраных может быть как культоргом так и казначеем

2×С(2,30)=2×30!/(228!2!)=2×(29×30/2)=2×435=870

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