A father said his son , " I was as old as you are at present at the time of your birth. " If the father age is 40 now, the son age 5 years back was  Options.
A) 14	B) 17	C) 15	D) 19	E) 99

Rationale: "let the son ' s present age be x years . then , ( 40 - x ) = x x = 20 . son ' s age 5 years back = ( 20 - 5 ) = 15 years answer : c"
Answer: C