Download HW Day #13 Answers

MAT 142 Summer Session 1
ANSWERS
Homework Day #13:
Name:______________________
I. Or and AND problems
A single die is rolled one time. Determine the probability of rolling …
1. an odd number or a number greater than 4
2
3
2. a number greater than 4 or less than two
1
2
3. a number greater than 3 or less than 5
1
One card is selected at random from a deck of playing cards. Determine the probability of selecting…
4. an ace or a 2
2
13
5. a jack or club
4
13
8
13
6. a picture card or a red card
3
4
7. a club or a red card
A GCC golf student has seven golf balls in his golf bag. 4 Titleist balls, 2 Top Flite balls and 1 Pinnacle ball. Two
balls are selected at random. Determine the probability of selecting each of the following first with replacement and
then second without replacement.
8. a Titleist and then a Pinnacle ball
with replacement:
4
49
without replacement:
2
21
without replacement:
10
21
without replacement:
11
21
without replacement:
0
9. no Top Flite ball
with replacement:
25
49
10. at least one Top Flite ball
with replacement:
24
49
11. two Pinnacle balls
with replacement:
1
49
12. Navigate to http://www.cut-the-knot.org/do_you_know/coincidence.shtml and scroll down the page partway
until you get to…
Following is an excerpt from
J.A.Paulos,
Beyond Numeracy
Read the contents of the page from this point down.
How many people are needed so that there is a 50% probability that one of them has a SPECIFIC BIRTHDATE (say
July 4th)?
“By contrast, 253 people are needed in order for the probability to be 1/2 that one of them has a specific
birth date, say July 4.”
13. Navigate to http://www.mathgoodies.com/lessons/vol6/challenge_vol6.html and work the ten problems on this
page. How many did you get correct?
Hopefully you said something like…. “I got 10 out of 10…I am such a good math student!”
14. Navigate to http://www.mathgoodies.com/puzzles2004/puzzles/iprobability1.html and try the interactive
probability crossword puzzle that you find on this page. It should be a good review of some of the terms we have
been using recently.
How did you do on the crossword puzzle? Hopefully you did okay. I f you filled it ALL in correctly you would
have got a message after completing the last correct word…”Congratulations you have solved the puzzle”.
II. Conditional Probability
15. A math teacher gave her class two tests. 25% of the class passed both tests and 42% of the class passed the first
test. What percent of those who passed the first test also passed the second test?
60%
16. A jar contains black and white marbles. Two marbles are chosen without replacement. The probability of
selecting a black marble and then a white marble is 0.34, and the probability of selecting a black marble on the first
draw is 0.47. What is the probability of selecting a white marble on the second draw, given that the first marble
drawn was black?
72%
17. The probability that it is Friday and that a student is absent is 0.03. Since there are 5 school days in a week, the
probability that it is Friday is 0.2. What is the probability that a student is absent given that today is Friday?
15%
18. At Kennedy Middle School, the probability that a student takes Technology and Spanish is 0.087. The
probability that a student takes Technology is 0.68. What is the probability that a student takes Spanish given that
the student is taking Technology?
13%
After you have tried 15 – 18 navigate to http://www.mathgoodies.com/lessons/vol6/conditional.html where you can
check your work and answers. You can also try the five problems at the bottom of the page for more practice!