SOLUTION: First of all, thaks for helping in advance... Here's the problem Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he j

Algebra ->  Probability-and-statistics -> SOLUTION: First of all, thaks for helping in advance... Here's the problem Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he j      Log On


   

Question 14625: First of all, thaks for helping in advance...
Here's the problem
Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he just answers each question randomly. What is the probability of his guessing all answers correctly?
I ended up with 1/512...but I started this a while ago and now I've forgotten how I got to that. Any help would be great.
Thanks,
Liz
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The probability of getting one answer right is 1/2
The probability of getting two right is 1/2 *1/2 = 1/2^2=1/4
You multiply because the events are independent; what you do
on one problem does not effect what you do on the next.
The prob of get all 10 right is (1/2)^10 = 1/1024
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Cheers,
Stan H.