Answer:
We know that in the box there are:
4 twix
3 kit-kat
Then the total number of candy in the box is:
4 +3 = 7
a)
Here we want to find the probability that we draw two twix.
All the candy has the same probability of being drawn from the box.
So, the probability of getting a twix in the first drawn, is equal to the quotient between the number of twix and the total number of candy in the box, this is:
p = 4/7
Now for the second draw, we do the same, but because we have already drawn one twix before, now the number of twix in the box is 3, and the total number of candy in the box is 6.
this time the probability is:
q = 3/6 = 1/2
The joint probability is the product of the individual probabilities, so here we have
P = p*q = (4/7)*(1/2) = 2/7
b) same reasoning than in the previous case:
For the first bar, the probability is:
p = 3/7
for the second bar, the probability is:
q = 2/6 = 1/3
The joint probability is:
P = p*q = (3/7)*(1/3) = 1/7
c) Suppose that first we draw a twix.
The probability we already know that is:
p = 4/7
Now we want another type, so we need to draw a kit-kat, the probability will be equal to the quotient between the remaining kit-kat bars (3) and the total number of candy in the box (6)
q = 3/6
The joint probability is:
P = p*q = (4/7)*(3/6) = 2/7
But, we also have the case where we first draw a kit-kat and after a twix, so we have a permutation of two, then the probability in this case is:
Probability = 2*P = 2*2/7 = 4/7
