Please explain your reasoning for number 21
A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
Section: Chapter Questions
Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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Please explain your reasoning for number 21
![19. An unfair coin with Pr[H]=.9 is tossed (indepen-
dently) 5 times. What is the probability that the
first, third, and fifth tosses are H, and all the others
are T?
(a) .0243
(b) .00243
(c) .243
(d) .0729
(e) .00729
(f) none of the others
20. Georgette labels her notebooks with a string of three
letters from the set {A,B,X,Y,Z}, and the first two
letters in each label must be distinct. (Acceptable:
АВА, ХҮА. Unacceptable:AAХ, ВВВ.) Нow many
different labels are there?
(а) 10
(b) 60
(c) 14
(d) 100
(е) 125
(f) none of the above
21. A multiple choice exam consists of 4 questions. Each
question has 5 possible answers, exactly one of which
is correct. Prstč decides to pick the answer to each
question at random. What is the probability that he
will get precisely two correct answers?
(а) .1024
(b) .9744
(c) .2048
(d) .1536
(e) .0256
(f) none of the above](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fae61d4f1-832a-4ede-b1d3-06ef4889bc0e%2F594f0a05-20fd-45c2-9519-88fce547c0d4%2Fqeg7eh_processed.jpeg&w=3840&q=75)
Transcribed Image Text:19. An unfair coin with Pr[H]=.9 is tossed (indepen-
dently) 5 times. What is the probability that the
first, third, and fifth tosses are H, and all the others
are T?
(a) .0243
(b) .00243
(c) .243
(d) .0729
(e) .00729
(f) none of the others
20. Georgette labels her notebooks with a string of three
letters from the set {A,B,X,Y,Z}, and the first two
letters in each label must be distinct. (Acceptable:
АВА, ХҮА. Unacceptable:AAХ, ВВВ.) Нow many
different labels are there?
(а) 10
(b) 60
(c) 14
(d) 100
(е) 125
(f) none of the above
21. A multiple choice exam consists of 4 questions. Each
question has 5 possible answers, exactly one of which
is correct. Prstč decides to pick the answer to each
question at random. What is the probability that he
will get precisely two correct answers?
(а) .1024
(b) .9744
(c) .2048
(d) .1536
(e) .0256
(f) none of the above
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