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?

Answer:25%

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

Answer: Probability is 0,2502822864 or 25.02822864 %.