Let's say you take a 10 question multiple choice test. Each question has 4 choices and you guess on all of them. What is the probability you get 7 or more right?

In a multiple choice question the probability of success is :  p = 1/4 = 0.25

and the probability of failure is : q = 3/4 =) 0.75

r = 7 ( correct answers )

Probability =  10 C r * ( 1/4 ) ^(10- r) * ˙( 3/4 )^r =

=  10 C 7 * ( 0.25 )^3 * ( 0.75 )^7 = 

= 120* 0,00208568572 =

= 0,2502822864

Probability is 0,2502822864 or 25.02822864 %.

b

step-by-step explanation:

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.