Additional
Probability
Problems
1) The American Red Cross says that
about 45% of the U.S. population has
Type O blood, 40% Type A, 11% Type
B, and the rest type AB.
Someone volunteers to give blood, what
is the probability that this donor
a)has Type AB blood?
b)has Type A or Type B?
4%
51%
c)has the complement of Type O? 55%
2) The American Red Cross says that
about 45% of the U.S. population has
Type O blood, 40% Type A, 11% Type
B, and the rest type AB.
Among four potential donors, what is the
probability that
a)all are Type O?
0.041
b)no one is Type AB?
0.849
c)at least one is Type B?
0.373
d) they are not all Type A?
0.974
3) A consumer organization estimates
that over a 1-year period 17% of
cars will need to be repaired only
once, another 7% need repairs twice,
and another 4% will require three or
more repairs.
If you own two cars, what is the
probability that
a)neither will need repair?
b)both will need repair?
.5184
.0784
4) A slot machine has three wheels that
spin independently. Each has 10 equally
likely symbols: 4 bars, 3 lemons, 2
cherries, and a bell. If you play, what is
the probability
a)you get 3 lemons?
.027
b)you get no fruit symbols?
.125
c)you get 3 bells (the jackpot)?
.001
d)you get no bells?
.729
e) you get at least one bar
(automatically lose)?
.784
5) Suppose the police operate a sobriety
checkpoint after 9 p.m. on a Saturday
night when national traffic experts
suspect about 12% of drivers have been
drinking. Trained officers can correctly
decide if a person has been drinking 80%
of the time. What’s the probability that
a)any given driver will be detained for
drunk driving?
.272
b)a driver who was detained has actually
been drinking?
.353
c) a driver who was released had
actually been drinking?
.033