Respuesta :
7.500 (rounded to 4 decimals) sum of the numbers on the balls.
Suppose we select two distinct balls
Then we have the following possibilities of selecting two balls
(2,2), (2,2) ............, i.e. 2 ways to get a sum of 4...............(2+2 = 4 and 2+2 = 4)
(2,5), (2,5), (5,2), (5,2), i.e. 4 ways to get a sum of 7...............(5+2 = 7 and 2+5 = 7)
(2,6), (2,6), (2,6), (2,6), i.e. 4 ways to get a sum of 8...............(2+6 = 8 and 6+2 = 8)
(6,5), (5,6) , i.e. 2 ways to get a sum of 11...............(5+6 = 11 and 6+5 = 11)
total number of possible outcomes = 2(for a sum of 4) + 4(for a sum of 7) + 4(for a sum of 8) + 2 (for a sum of 11)
= 2 + 4 + 4+2
= 12
So, P(getting a sum of 4) = (number of ways to get a sum of 4)/total number = 2/12
similarly,
P(getting a sum of 7) = (number of ways to get a sum of 7)/total number = 4/12
P(getting a sum of 8) = (number of ways to get a sum of 8)/total number = 4/12
P(getting a sum of 11) = (number of ways to get a sum of 11)/total number = 2/12
We know that expected value E[x] = sum of all individual sum values by their respective probability
= 4*(2/12) +7*(4/12) +8*(4/12) +11*(2/12)
= 0.6667 + 2.3333 + 2.6667 + 1.8333
= 7.500 (rounded to 4 decimals)
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