Answer: a) 0.003
b) 0.125
c) 0.047
Step-by-step explanation:
We have a set of 8 numbers {1,2,...,8}
Let's analyze each case:
a) 5 and 8 are picked. The probability here is:
In the first selection, we have two possible picks (we can pick 5 or 8), so we have two possible outcomes out of 8 total outcomes, the probability for the first selection is:
P = 2/8 = 1/4.
Now, if one of those numbers was picked in the first selection, only one outcome is possible in this second selection, (if before we picked a 5, here we only can pick an 8, or if in the first selection we picked an 8, here we only can pick a 5.)
the probability is:
P = 1/8
The joint probability is equal to the product of the individual probabilities, so here we have:
P = (1/4)*(1/8) = 1/32 = 0.003
b) The numbers match (we draw two sixes, for example) :
In the first selection, we can have any outcome (the only requirement is that in the second selection we pick the same outcome), so the probability is:
P = 8/8 = 1
in the second selection, we can have only one outcome, so here the probability is:
P = 1/8
The joint probability is p = 1/8 = 0.125
c) The sum is smaller than 4:
The combinations are:
1 - 1 , 1 - 2 and 2 - 1
We have 3 combinations, and the total number of possible combinations is:
8 options for the first number and 8 options for the second selection:
8*8 = 64
The probability is equal to the number of outcomes that satisfy the sentence (3) divided by the total number of outcomes (64):
P = 3/64 = 0.047
