the average age of 3 boys is 15 years and their ages are in proportion 3 : 5 : 7 . what is the age in years of the eldest boy ? Choose the most appropriate option.
A) 6	B) 9	C) 16	D) 4	E) 21

Rationale: 3 x + 5 x + 7 x = 45 x = 3 7 x = 21 answer : e
Answer: E