1)An alloy of copper and tin is 20% copper . How many pounds of copper must be added to 20 pounds of the allay in order for the resulting alloy to be 50% copper ?a)6b)12c)12.5d)13e)142)A solution of 27 gallons of acid contains 9 gallons of pure acid . how much water in gallons, should be added to produce a 25 percent solution of this acid ?a) 6 and 3/4b)9c)15 and 3/4d)18e)27please explain the answer
If an alloy is 20% copper that means that 1/5 of it is copper. 20/5=4 so 4lbs of it is copper and the rest is 16lbs of tin. In order for the alloy to be 50% copper there must be equal parts tin and copper, therefore, 12 lbs of copper must be added so there is 16lbs of tin and 16lbs of copper. In order for a solution of acid to be 25% acid there must be three gallons of water for every 1 gallon of acid. So if there is 9 gallons of acid there must be 27 gallons of water for a total of 36 gallons solution. There is only 27 gallons off solution, therefore 9 gallons of water must be added. TL;DR: Both answers are B
1) 0.2*20 + x = 0.5(x+20) 0.5x = 6 x = 12 lb Answer b) 2) 0.25 = 9/(x+27) 0.25x + 6.75 = 9 x = 9 gallons Answer b)
