a goldsmith added 10% impurities to 50m of pure gold later he took 25gm of the above gold& added 10gm of pure gold to it what % of impurity was there in the 40gm of gold?

• Gold Impurity Total
  50 5 55
  
  Gold:Impurity is 50/5 i.e. 10:1
  
  As 25gms of gold is withdrawn from total of 55, amount of gold left with us is 30gms. As 25 gms of gold is not all pure gold it contains impurity, amount of impurity is 25*(1/11).
  
  Remaining impurity is 5-25/11 = 30/11.
  
  And then question says that 10gm of gold is added so total gold becomes 30+10 = 40gms
  
  Now, this 40 gms of gold contains 30/11 gms of impurity. Now, to find 30/11 gms is what % of 40gms, i do
  
  ((30/11)/40)*100 = 75/11 = 6.9%
  
• 7 years agoHelpfull: Yes(2) No(2)
• 8.33%
  
  (I) with 10% impurities in 50gm. of pure gold: Amount of Gold : Impurities= 50 :5
  (II) 25 gm of this gold will contain Gold : Impurities=25*50/55 : 25*5/55=250/11 : 25/11 and
  (III) Remaining 30 gm will contain Gold : Impurities=30*50/55 : 30*5/55= 300/11 : 30/11
  (IV) As 10 gm of pure gold is added to 25 gm (or mixture II) above, it will contain Gold : Impurities=(250/11)+10 : 25/11= 360/11 : 25/11
  (V) Now the total mixture of 65 gm (III+IV) will contain Gold:Impurities=(300/11)+(360/11) : (30/11)+(25/11)
  =660/11 : 55/11 i.e % of impurities=100*55/660=25/3=8.33
  So 40 gm of gold will contain impurities=40*8.33/100=3.33 gm
• 8 years agoHelpfull: Yes(0) No(3)