There are 500 coins of Rs. 1, Rs 2, and Rs 5. The sum of amount of coins is 960. If number of coins of 1 rupee and 5 rupee interchanged the amount will be 480. Then what will be the number of coins of Rs.2 ?

• 1).let x,y,z be variables for 1,2 and 5 rs. coins, it represents the total number of coins.
  1st equation:- x+y+z=500
  2). now, by multiplying each weight with it's respective variable , we'll get the total amount of 960 rs.
  2nd equation:- x+2*y+5*z=960
  3). now just interchange the constants 1 and 5
  3rd equation:- 5*x+2*y+z=480
  
  by solving these three equations we'll get y=260,
  the total number of coins of 2 rs. is 260
  
  after this we can validate the answer by putting the value of x,y,z in any of the three equations.
  we don't need to remember which variable represents which coin, just by looking at the 2nd equation you'll get it.
  the method is also useful in many other applications too.
• 8 years agoHelpfull: Yes(0) No(0)
• x no 1 rupee coins, y no 2 rupee coins & z no 5 rupee coins
  x+2y+5z=960 x+y+z=500
  z+5x=480
  
  from 1,2&3 we get
  
  x+2(500-x-z)+z=500
  x+1000-2x-2z +z=500
  -x-z+500=0
  x+z=500 ----- (4)
  
  So, y=0
• 7 years agoHelpfull: Yes(0) No(0)