шестое чувство

[barzel]

В эксперименте участвовало 30 слепых. Каждого слепого привели в закрытую комнату и поставили его напротив 5 цветных ящиков(цвета разные). Каждому слепому были выданы 5 записок в соответствии с цветом ящика, и попросили каждого из них подобрать правильный ящик к записке.
Перед вами результаты эксперимента:
Каждый из них сумел подобрать по крайней мере одну записку.
10 смогли ровно одну
6 смогли ровно две
4 смогли ровно 3

Вопрос: сколько людей смогло подобрать ровно 4? и сколько ровно 5?

Comments

[barzel.livejournal.com]

второй это я, просто не было сил регистрироваться

[(Anonymous)]

Ouch, forgot to choose Anonymous...

[(Anonymous)]

This problem has several right answers: N+/-9, N+/-7, etc.

[barzel.livejournal.com]

it isn't right, think more, here isn't any probability

[(Anonymous)]

Ok, we know that only 9 folders will change their original state, e.g. 1, 4, 9, 16, etc.

Now, let's assume that all these 9 were open originally. Obviously, the number of open books would be now N-9.

Now, say 1st was closed originally and other 8 were open. After we change the state, the 1st would be open and 8 closed. So, the number of open folders will decrement by 7.

Repeating the same train of thoughts will have +-5, +-3, etc.

Do you see a logic error in these explanations?

[barzel.livejournal.com]

the answer is that folders no. 1, 4, 9, 16,25 etc will change their status, because square of number has odd number of multiplies, that is why it change, rest folder will return to initial status. you solved id right.

[(Anonymous)]

I actually gave the wrong answer, because I forgot 100th person. E.g. the difference would be 10.