Question

У коробцi 5 поплавцiв:2 синiх i 3 червонi.Скiльки поплавцiв треба взяти з коробки,не заглядаючи в неï,щоб серед них був хоча би 1 червоний

Answer 1

3 поплавка нужно взять из коробки. 

Answer 2

Problem Analysis

To solve this problem, we need to determine the minimum number of floats to be taken from the box without looking into it, so that at least one of them is red.

Solution

The minimum number of floats to be taken from the box without looking into it to ensure at least one is red can be found using the concept of complementary events.

The probability of not drawing a red float from the box is the probability of drawing all blue floats. Therefore, the probability of not drawing a red float is (2/5) * (1/4) * (1/3) = 1/10.

So, the probability of drawing at least one red float is 1 - 1/10 = 9/10.

Therefore, to ensure at least one red float, we need to take 4 floats from the box without looking into it.

Final Answer

To ensure at least one red float without looking into the box, you need to take 4 floats from the box.