The average age of 4 boys is 25 years and their ages are in the proportion 3:5:7. The age of the youngest boy is? Choose the correct choice from the following options: A) 10years B) 15years C) 20years D) 25years E) 18years
Total age of 4 boys = 25*4= 
<gadget id="calculator">25*4</gadget>
<output>100</output>
100   ratio of their ages= 3:5:7   Age of the youngest = 100*3/15= 
<gadget id="calculator">100*3/15</gadget>
<output>20</output>
20 years   Answer is 20years
<result>C</result>
The average age of 4 boys is 25 years and their ages are in the proportion 3:5:7. The age of the youngest boy is?