Probability when seleting balls from an urn

[dperkovic]

Homework Statement

There is total of 300 balls in the basket, 30 of them is red (rest is white). If we picked up, randomly, 4 balls, what is the probabilty that all of them is red ?


2. The attempt at a solution

For one picked ball, probability that it's red is 30/300 = 1/10.
If picked ball is red, probabilty for next ball is 29/299,and so on, 28/298, 27/297.

Is that correct ? And, what next ?

 

[Maybe_Memorie]

Homework Statement

There is total of 300 balls in the basket, 30 of them is red (rest is white). If we picked up, randomly, 4 balls, what is the probabilty that all of them is red ?


2. The attempt at a solution

For one picked ball, probability that it's red is 30/300 = 1/10.
If picked ball is red, probabilty for next ball is 29/299,and so on, 28/298, 27/297.

Is that correct ? And, what next ?

Yup, that's right so far.
In probability, what is the relationship with "And" events?

 

[dperkovic]

Yup, that's right so far.
In probability, what is the relationship with "And" events?

P(A and B) = P(A) x P(B) ?

 

[dperkovic]

P(A and B) = P(A) x P(B) ?

P(A and B) = P(A) x P(B after A) is correct,because this is depended events, is that true ?

If it is, the solution would be: 30/300 * 29/299 * 28/298 * 27/297.

 

[Maybe_Memorie]

Exactly.