The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?
Select
A) 6  B) 9  C) 8  D) 4  E) 2
3x + 5x + 7x = 45   x =3   3x = 9   Answer: 9
<result>B</result>
The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?