A father said to his son, "I was as old as you are at present at the time of your birth." If the father's age is 40 years now, the son's age 10 years back was?
Choose the correct choice from the following answers.
A) 12yr
B) 15yr
C) 14yr
D) 10yr
E) 20yr
Let the son's present age be x years   Then, 40-x = x   x = 20   Son's age 10 years back = 20-10= 
<gadget id="calculator">20-10</gadget>
<output>10</output>
10years   Answer is 10yr
<result>D</result>
A father said to his son, "I was as old as you are at present at the time of your birth." If the father's age is 40 years now, the son's age 10 years back was?