A bag contains some number of marbles. It is known that 20 of them are red. When 15 marbles are drawn, without replacement, we get 6 red. Assuming E(X)=6 red, what is the total number of marbles in the bag?

The total number of marbles in the bag is 50.

Step-by-step explanation:

Here, we have n trials, without replacement. So the hypergeometric distribution is used.

The mean of the hypergeometric distribution is:

In which n is the number of items in the sample, k is the number of items in the population that are classified a success and N is the size of the population.

15 marbles are drawn:

This means that

A bag contains some number of marbles. It is known that 20 of them are red.

This means that , since a success is drawing a red marble.

Assuming E(X)=6 red, what is the total number of marbles in the bag?

We have to find N when

So

The total number of marbles in the bag is 50.

answer: 180

step-by-step explanation:

12-2=10

20-2=18

18x10=180

you never say the total so we cant find the percentage used for petrol

step-by-step explanation: