text: # An alloy contains the copper and aluminum in the ratio of 7 : 4
  
  ## d) 14.4 kg
  
  Solution -
  
  Copper and Aluminum in the ratio = 7 : 4
  
  Let,
  
  Copper and Aluminum be 7x and 4x respectively in the weapons.
  
  Aluminum in the weapon = 12 kg (given)
  
  4x = 12
  
  x = 3
  
  Therefore,
  
  Copper in the Weapon = 7x
  
  Copper in the weapon = 7*3
  
  Copper in the weapon = 21 kg
  
  Total Alloy in the weapon = 12 + 21
  
  Total Alloy in the weapon = 33 kg
  
  12% of the alloy got destroyed.
  
  Now,
  
  Total alloy in the weapon = (100% - 12%)
  
  Total alloy in the weapon = 88%
  
  But,
  
  Total alloy in the weapon = 33kg
  
  88%  = 33kg
  
  1% = (33/88)
  
  1% = (3/8)
  
  100% = [(3/8)*100]
  
  100% = 300/8
  
  100% = 37.5
  
  Therefore,
  
  Weight of the alloy required is 37.5
  
  Hence,
  
  The correct option is (c) 37.5
  
  Thank You