A fold density is 19 times greater than the water and for copper it is 9 times. At what ratio you can mix gold
and copper to get 15 times denser than water. ?
Ans: 3 : 2

• Ans. 3 : 2
  
  Suppose x units of gold are mixed with y units of copper to make (x+y) units of alloy which is 15 times denser than water.
  
  Then 19*x + 9*y = 15*(x + y)
  => 19*x - 15*x = 15*y - 9*y
  => 4*x = 6*y => x/y = 3/2
  So gold and copper should be mixed respectively in the ratio of 3 : 2
• 13 years agoHelpfull: Yes(40) No(5)
• This can be solved using Allegation method:
  The first value is of Gold which is 19 times denser.
  The second value is of copper which is 9 times denser.
  The ratio to find is 15 times denser...call this as middle value.
  So now, Formula is direct in one step:
  (second value-middle) : (first value-middle) ie (9-15):(19-15) ...avoid negative sign.
  ie. 6:4
  ie. 3:2
• 10 years agoHelpfull: Yes(12) No(0)
• Allegation mixture Rule:
  
  19 times greater than the water for copper it is 9 times
  /
  /
  /
  mean= 15
  /
  /
  (15-9) =6 / (19-5)=4
  Now 6/4 after division it would 3/2 which is 3:2
  
• 8 years agoHelpfull: Yes(0) No(0)
• given- 19+9=15
  use algebirc rule15-9=19-15
  6=4
  3/2
  
• 8 years agoHelpfull: Yes(0) No(0)