My grandson is about as many days as my son in weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 140 years. Can you tell me my age in years?
A. 80
B. 90
C. 85
D. 84
E. 89

• This problem is conveniently solved by writing down the necessary equations. Note that there are 12 months in a year, 52 weeks in a year, and 365 days in a year.
  
  Let m be my age in years. If s is my son's age in years, then my son is 52s weeks old. If g is my grandson's age in years, then my grandson is 365g days old. Thus,
  
  365g = 52s.
  
  Since my grandson is 12g months old,
  
  12g = m.
  
  Since my grandson, my son and I together are 140 years,
  
  g + s + m = 140.
  
  The above system of 3 equations in 3 unknowns (g, s and m) can be solved as follows.
  
  m / 12 + 365 m / (52 × 12) + m = 140 or
  
  52 m + 365 m + 624 m = 624 × 140 or
  
  m = 624 × 140 / 1041 = 84.
• 12 years agoHelpfull: Yes(2) No(0)