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? Choose the correct choice from the following
A) 8  B) 9  C) 7  D) 6  E) 5
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?