Spam and Lake have the mission
to destroy the
Star Joke
. Spam’s
probability of success on any given
try is .7, while Lake’s is .8. Spam
and Jake will each be able to make
just one try, and they decide that
Spam will be first. What is the
probability that the
Star Joke
is in
fact destroyed?
(A) it cannot be determined
(B) .95
(C) .8
(D) .56
(E) .94
(F) none of the above

Question

Spam and Lake have the mission
to destroy the
Star Joke
. Spam’s
probability of success on any given
try is .7, while Lake’s is .8. Spam
and Jake will each be able to make
just one try, and they decide that
Spam will be first. What is the
probability that the
Star Joke
is in
fact destroyed?
(A) it cannot be determined
(B) .95
(C) .8
(D) .56
(E) .94
(F) none of the above

anonymous · Answer

P(success) = P(Spam success) + P(Spam fails jake Success)
P(success) = 0.7 + 0.8(0.3) = 0.94
E

We don't care what happens if Spam's success, so you don't multiply his success rate by anything.