The average age of 5 boys is 25 years and their ages are in the proportion 3:5:7. The age of the youngest boy is? Pick:
A) 10years B) 15years C) 20years D) 25years E) 18years
Total age of 5 boys = 25*5= 
<gadget id="calculator">25*5</gadget>
<output>125</output>
125   ratio of their ages= 3:5:7   Age of the youngest = 125*3/15= 
<gadget id="calculator">125*3/15</gadget>
<output>25</output>
25 years   Answer is 25years
<result>D</result>
The average age of 5 boys is 25 years and their ages are in the proportion 3:5:7. The age of the youngest boy is?