Question 255295
what is the problability of getting all four problems right on a test with 4 differnet possible answers? what is the problability of getting at least one problem rgiht? 
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Expansion of (c+w)^4 gives all the probabilities.
.
a)
Let c=probability of guessing correctly =.25 
w= prob. of guessing wrongly=.75
c^4=.25^4=.0039
.
b)
1-w^4 One minus prob. that all are wrong.
=1-.75^4
=1-.3164
=.6836
.
Ed