Предмет: Алгебра, автор: devo4kalapo4ka

. Сколько среди 9-значных чисел, образованных из цифр 1, 2, 3, ..., 9 без их повторения, таких, в которых цифры 2 и 5 стоят рядом ?

Ответы

Автор ответа: chooooko

Ответ:

294 чисел

Объяснение:

251346789, тут местами могут поменяться 1 и 3, 1 и 4, 1 и 6, 1 и 7, 1 и 8, 1 и 9, 3 и 4, 3 и 6, 3 и 7, 3 и 8, 3 и 9, 4 и 6, ... 8 и 9. Всего так можно поменятся 21 раз. Не забудем, что можно еще менять место 25: 125346789, 132546789, 134256789, 134625789, 134672589, 134678259, 134678925, то есть 7 штук, умножаем 7 на 21=147, также можно эти 25 поменять местами и получить 52, тогда вариантов становиться в 2 раза больше, 147*2=294 вариантов.

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