# how much of a 90% acid solution must be added to 48 mL of a 20% solution to produce a 50% solution of acid?

In general:fraction of the substance x amount of mixture = amount of the substance. Example 1:How many gallons of a 12% solution should be combined with 10 gallons of an 18% solution to obtain a 16% solution? (sum of parts = whole!)12x + 18(10) = 16(x + 10) can forget % since in all terms! 6x + 90 = 8(x + 10) 6x + 90 = 8x + 80 -2x = -10 x = 5 (5 gallons) Example 2:Alloy A is 1 part copper to 3 parts tin. Alloy B is 1 part copper to 4 parts tin. How much of alloy B should be added to 24 pounds of alloy A to obtain an alloy that is 2 parts copper to 7 parts tin? Alloy A: copper Alloy B: copper Mixture: copper A B Mixture (24)+ x = (x + 24) 6 + x = (x + 24) 270 + 9x = 10(x + 24) 270 + 9x = 10x + 240 30 = x 30 lb.Answers:1) 54 gallons2) 1 gallon3) 8 ounces4)gallons or 1 gallons5) % or 15%6) 54 pounds7) gallons or 3 gallons8) gallons or 1 gallons9) ounces or 33 ounces