The probability that you will guess the first answer correctly = 1/2 = 0.5
The probability that you will guess the second answer correctly = 1/2 = 0.5
The probability that you will guess the third answer correctly = 1/2 = 0.5
The probability that you will guess all three answers correctly is
(0.5) x (0.5) x (0.5) = 0.125 = 12.5% .
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Here are all the ways your answer sheet could wind up:
(R = a right answer. W = a wrong answer.)
W W W
W W R
W R W
W R R
R W W
R W R
R R W
R R R
Number of possible ways to score 0 right out of 3 questions: 1 way
Number of possible ways to score 1 right out of 3 questions: 3 ways
Number of possible ways to score 2 right out of 3 questions: 3 ways
Number of possible ways to score 3 right out of 3 questions: 1 way
Statistically, if your answers are all pure guesses,
then on the average, the score you expect is
(0 + 33-1/3 + 33-1/3 + 33-1/3 + 66-2/3 + 66-2/3 + 66-2/3 + 100) / 8
= 400 / 8
= 50% .
If you're happy with that score, great !
Go to the movies the night before the test,
and start guessing.