In a large bag of marblesb20% of them are red. A child chooses 4 marbles. If the child chooses the marbles at random what is the chance of getting three exact red marble

Step-by-step explanation:

Here, let us assume that the total number of the marbles in the bag = m

Now, as given :

The total percentage of red marbles in bag = 20% of m  

So, total red marbles   =  0.2 m

Marbles which are not red  = m - 0.2 m = 0.8 m

The number of marbles chosen at random = 4

Now, probability of getting first red marble  =

Again, total marbles left = m - 1

Probability of getting second red marble  =

Again, total marbles left = m - 2

Probability of getting third red marble  =

Again, total marbles left = m - 3

Probability of getting fourth non - red marble  =

So, the probability if 3 marbles being red and 1 non red

=