A 30 question multiple choice test consists of 20 questions with four answer choices each and 10 questions with five answer choices each. What is the expected number of correct answers that would result from random guessing?
You would expect to get 1/4 of the 20 and 1/5 of the 10; so expected number = 20/4 + 10/5 = 5+2 = 7
What is the rule and ratios?
