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?
Pick one.
A) 6
B) 9
C) 6
D) 4
E) 1
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?