A man can feed himself for a certain number of days with Rs.1200. If his cost per day increases by Rs.20, he can feed himself for 30 days less. Find the number of days he used to feed himself earlier.

• Ans :40
  
  Let the number of days with cost per day increasing be n. Then, the number of days with cost per day constant will be n+30.
  
  Let x be cost every day.
  
  (n+30)*x = 1200
  
  With increase in cost the series becomes x, x+20, x+40..... n terms
  
  Thus the sum = (n/2)*(2x+(n-1)*20) = 1200
  => (n^3) + 29*(n^2) -30(n) -3600 =0
  
  Solving the above equation n=10
  
  Thus number of days he used to feed himself earlier was (n+30) = 40
• 12 years agoHelpfull: Yes(3) No(5)
• let x= no. of day
  y= cost per day
  
  xy=1200 ...............eq(1)
  (x-30)(y+20)=1200.......eq(2)
  
  solving 2 eq we get x=60
• 11 years agoHelpfull: Yes(1) No(1)