Answer
$P(E)=\frac{9}{45}=0.2$
Work Step by Step
Consider for simplicity that:
A = The Screamin’ Eagle
B = The Boss
C = River King Mine Train
D = Batman the Ride
E = Mr. Freeze
F = Ninja
G = Tony Hawk’s Big Spin
H = Evel Knievel
I = Xcalibur
J = Sky Screamer
Event = "Ethan will ride the Screamin’ Eagle" = {AB, AC, AD, AE, AF, AG, AH, AI, AJ}. So, $N(E)=9$.
Sample space: S = {AB, AC, AD, AE, AF, AG, AH, AI, AJ, BC, BD, BE, BF, BG, BH, BI, BJ, CD, CE, CF, CG, CH, CI, CJ, DE, DF, DG, DH, DI, DJ, EF, EG, EH, EI, EJ, FG, FH, FI, FJ, GH, GI, GJ, HI, HJ, IJ}. So, $N(S)=45$.
Using the Classical Method:
$P(E)=\frac{N(E)}{N(S)}=\frac{9}{45}=0.2$
