1-4.5 A company manufactures small electric motors having horse power ratings of 0.1, 0.5, or 1.0 horsepower and designed for operation with 120 V single-phase ac, 240 V single-phase ac, or 240 V three-phase ac. The motor types can be distinguished only PROBLEMS 41 by their nameplates. A distributor has on hand 3000 motors in the quantities shown in the table below. Horsepower 120 V ac 240 V ac 240 V 30 0.1 900 400 0 0.5 200 500 100 1.0 100 200 600 One motor is discovered without a nameplate. For this motor determine the probability of each of the following events. a) The motor has a horsepower rating of 0.5 hp. b) The motor is designed for 240 V single-phase operation. c) The motor is 1.0 hp and is designed for 240 V three-phase operation. d) The motor is 0.1 hp and is designed for 120 V operation. 1-4.6 In Problem 1-4.5, assume that 10% of the motors labeled 120 V single-phase are mismarked and that 5% of the motors marked 240 V single-phase are mismarked. a) If a motor is selected at random, what is the probability that it is mismarked? b) If a motor is picked at random from those marked 240 V single-phase, what is the probability that it is mismarked? c) What is the probability that a motor selected at random is 0.5 hp and mismarked? 1-4.7 A box contains 25 transistors, of which 4 are known to be bad. A transistor is selected at random and tested. a) What is the probability that it is bad? b) If the first transistor tests bad what is the probability that a second transistor selected at random will also be bad? c) If the first transistor tested is good, what is the probability that the second transistor selected at random will be bad?
1-4.5 A company manufactures small electric motors having horse power ratings of 0.1, 0.5, or 1.0 horsepower and designed for operation with 120 V single-phase ac, 240 V single-phase ac, or 240 V three-phase ac. The motor types can be distinguished only PROBLEMS 41 by their nameplates. A distributor has on hand 3000 motors in the quantities shown in the table below. Horsepower 120 V ac 240 V ac 240 V 30 0.1 900 400 0 0.5 200 500 100 1.0 100 200 600 One motor is discovered without a nameplate. For this motor determine the probability of each of the following events. a) The motor has a horsepower rating of 0.5 hp. b) The motor is designed for 240 V single-phase operation. c) The motor is 1.0 hp and is designed for 240 V three-phase operation. d) The motor is 0.1 hp and is designed for 120 V operation. 1-4.6 In Problem 1-4.5, assume that 10% of the motors labeled 120 V single-phase are mismarked and that 5% of the motors marked 240 V single-phase are mismarked. a) If a motor is selected at random, what is the probability that it is mismarked? b) If a motor is picked at random from those marked 240 V single-phase, what is the probability that it is mismarked? c) What is the probability that a motor selected at random is 0.5 hp and mismarked? 1-4.7 A box contains 25 transistors, of which 4 are known to be bad. A transistor is selected at random and tested. a) What is the probability that it is bad? b) If the first transistor tests bad what is the probability that a second transistor selected at random will also be bad? c) If the first transistor tested is good, what is the probability that the second transistor selected at random will be bad?
A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
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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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Transcribed Image Text:1-4.5 A company manufactures small electric motors having horse power ratings of 0.1,
0.5, or 1.0 horsepower and designed for operation with 120 V single-phase ac, 240 V
single-phase ac, or 240 V three-phase ac. The motor types can be distinguished only
PROBLEMS
41
by their nameplates. A distributor has on hand 3000 motors in the quantities shown in
the table below.
Horsepower
120 V ac
240 V ac
240 V 30
0.1
900
400
0
0.5
200
500
100
1.0
100
200
600
One motor is discovered without a nameplate. For this motor determine the probability
of each of the following events.
a) The motor has a horsepower rating of 0.5 hp.
b) The motor is designed for 240 V single-phase operation.
c) The motor is 1.0 hp and is designed for 240 V three-phase operation.
d) The motor is 0.1 hp and is designed for 120 V operation.
1-4.6 In Problem 1-4.5, assume that 10% of the motors labeled 120 V single-phase are
mismarked and that 5% of the motors marked 240 V single-phase are mismarked.
a) If a motor is selected at random, what is the probability that it is mismarked?
b) If a motor is picked at random from those marked 240 V single-phase, what is the
probability that it is mismarked?
c) What is the probability that a motor selected at random is 0.5 hp and mismarked?
1-4.7 A box contains 25 transistors, of which 4 are known to be bad. A transistor is selected
at random and tested.
a) What is the probability that it is bad?
b) If the first transistor tests bad what is the probability that a second transistor selected
at random will also be bad?
c) If the first transistor tested is good, what is the probability that the second transistor
selected at random will be bad?
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