SOLUTION: A test consists of fifteen true/false questions. A student who forgot to study guesses randomly on every question. What is the probability that the student answers exactly five

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Question 1106041: A test consists of fifteen true/false questions.
A student who forgot to study guesses randomly
on every question. What is the probability that
the student answers exactly five questions
correctly?
Found 2 solutions by Boreal, josmiceli:
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
This is 15C5, the number of ways 5 can be correct from 15, *(1/2)^5*(1/2)^10=0.0916

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+2%5E15+ is the number of possible test results
The number of test results with +5+ correct answers is:
C( 15,5 ) = +15%21+%2F+%28%28+15+-+5+%29%21+%2A+5%21+%29+
C( 15,5 ) =
C( 15,5 ) = +%28+15%2A14%2A13%2A12%2A11+%29+%2F+%28+5%2A4%2A3%2A2%2A1+%29+
C( 15,5 ) = +%28+14%2A13%2A12%2A11+%29+%2F+8+
C( 15,5 ) = ++7%2A13%2A3%2A11+
C( 15,5 ) = +3003+
+3003+%2F+2%5E15+
( I lost my calculator -you can calculate )