Ned got an overall grade of 86 percent because if each question is 4 points, then 6×4=24 but if he got a bonus 10 points, then you can do 24-10=14 and then you do 100-14 which equals your answer: 86.
Solution :
Given :
X = the number of boys in a family of four children
Families having four children are chosen randomly.
The gender distribution in the four child family are equally probable.
Thus,
X P(X) CDF
0
= 1/16 
1
= 1/4
2
= 3/8 
3
= 1/4 
4
= 1/16 1
Answer: it’s 55/100 percent