Question 985628
 
Given:
A class of 40 students.
Probability of a student being >= years old = 0.8
 
Solution:
number of students, n = 40
probability of a student being not >=13 years old, p
= probability of a student being < 13 years old = 1-0.8 = 0.2
Expected value = np = 40 * 0.2 = 8
 
Answer: Eight students are expected to be under 13.