Problem on ages

Question

10 years ago Jones age was 5 years more than that of his son.5 years hence the ratio of their ages will be 10:9. Find their present ages.

Answer 1

Let these folks have ages J and S, NOW.  ten years ago Jones' age was J-10 = S - 10 + 5.  Therefore S = J - 5...(*)

 

5 YEARS HENCE (i.e. from now) their ages will be J+5 & S +5 and the ratio will be 10:9 = (J+5):(S+5).

Cross-multiplying this proportion gives 10S + 50 = 9J +45 or 10S = 9J - 5.

 

Into this we substitute from (*) to get 10(J-5) = 9J-5; this leads to J =45, S = 40 (now).

 

That's the mathematical solution, but I don't think that it passes the BIOLOGICAL TEST. Maybe that's a stepson or adopted son.