3 pens, 5 pencils and 7 erasers cost Rs. 49 while 5 pens ,8 pencils and 11 eraser cost Rs. 78 . find the cost (in Rs.) of 3 pen, 3 pencils and 3 erasers ?

• Rs. 27
  
  Let cost of each pen, pencil and eraser be Rs. x, y and z respectively, then
  3x + 5y + 7z = 49 ---(i) and
  5x + 8y +11z =78 ---(ii)
  Multiplying eqn. (i) by 5 & (ii) by 3 and then subtracting (ii) from (i), we get y + 2z = 11 ---(iii)
  Here (y,z) satisfying condition can be (1,5) (3,4) (5,3) (7,2) (9,1)
  But only y=5, z=3 with x=1 satisfies the condition in eqn (i) or (ii)
  So cost of 3 pen, 3 pencils and 3 erasers = 3x+3y+3z = 3(x+y+z) = 3(1+5+3) = Rs. 27
• 7 years agoHelpfull: Yes(6) No(5)
• pens pencils erasers
  5 8 11 78
  3 5 7 49
  2 3 4 29
  1 2 3 20
  1 1 1 9
  
  3 3 3 27
• 7 years agoHelpfull: Yes(3) No(3)