What is the average number of questions answered

Question

There are 50 question on a quiz given to a class of student . Only 20% of the class answered all the questions on the quize . Of the remaining students , half answered two_fifths of the questions and the other half answered three_fifths . What was the average number of questions answered on this quiz

Answer 1

.2 answered 50 questions

 

.4 answered 20 questions

 

.4 answered 30 questions

 

Because, 1 - .2 = .8, the remaining students; half of .8 = .4

 

And 2/5 of 50 = 20, and, 3/5 of 50 = 30

 

So,

 

let's just say there are 10 students, because that makes the math easy:

 

 

(2 x 50) + (4 x 20) + (4 x 30) all divided by 10 ( which is the number of students)

 

(100 + 80 + 120)/10 = 300/10 = 30, the average score