Question 13320
72 degrees is 1/5 of the total of a circle (360)
144 degrees is 2/5.
36 degrees is 1/10
108 degress is 3/10


So,
P(blue) = 0.2
P(green) = 0.4
P(yellow) = 0.1
P(red) = 0.3


--> total is 1, so that is correct.


Now for the questions:

P(red then green) 
--> P(red) and P(green)
0.3 * 0.4
0.12
12%


P(once red and once green)
--> P(red then green) OR P(green then red)
0.12 + 0.12
0.24
24%


P(A) = 0.4
P(B) = 1-0.4
--> P(B) = 0.6


P(A union B) means the probability of (A or B), well the spinner has to be green or not green (the definitions of A and B) so, P(A union B) = 1, so P(A not union B) must be 0, ie impossible


As for part d. Event A and event B are mutually exclusive --> if A happens then B cannot.


For 2 events that are mutually exclusive, they cannot be independent.


jon.