SOLUTION: A test consists of 10 true-or-false questions. If a student randomly chooses answers for each question, find the probability that the student: Answers at least 1 question correct

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Question 369622: A test consists of 10 true-or-false questions. If a student randomly chooses answers for each question, find the probability that the student:
Answers at least 1 question correctly. (3 decimals)
I got 2^10 = 1,024
I did this way, but does not work, very close...
C(10,1)/1024 =
10/1024 = .00976
The answer is 0.999 but how?


Found 2 solutions by Fombitz, edjones:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Find the probability that the student answers none correctly.
P(none)+P(not none)=1
P(not none)=1-P(none)
So "not none" means he answer at least one correctly... up to and including all 10 correctly
.
.
.
P(none)=%280.5%29%5E10=0.0009765625
P(not none)=1-0.0009765625
P(not none)=0.9990234

Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
Let x=.5 probability of getting a problem wrong.
1- probability that he gets them all wrong = the probability that the student answers at least 1 question correctly.
1-.5^10=.9990
.
Ed