Download Lesson Three Basic Probability Practice File

Probability Practice
Suppose a coin is bent so that the probability of its coming up “heads” on
any toss is 2/5. If the coin is tossed 3 times, find the probability of getting:
a) 1 “head”
b) 0 “heads”
c) 2 “heads”
54
P(1 head)  125
Answer:
27
P(0 heads)  125
36
P(2 heads)  125
A bag contains four red balls, three blue balls and three white balls.
If I reach into the bag and pull out two balls, without replacement,
what is the probability that I pull out two blue balls or a red ball then
one white ball?
Answer:
P
1
5
A boy has a probability of 0.3 of hitting a target with his rifle. Find the
probability that he first hits the target with his third shot.
Answer: 0.147
The numbers 1, 2, 3 and 4 are written on separate sheets of paper and
placed in a hat. Two slips of paper are drawn, one after the other
without replacement. Using a tree diagram, find the probability that the
sum of the numbers picked is 6 or more.
Answer:
P
1
3
For the events A and B, if
find P(A  B) .
Answer:
P(A  B)  0.4
P(A)  0.6 and P(B)  0.8 , and P(A  B)  1