You need 630 mL of a 50% alcohol solution. On hand, you have a 10% alcohol mixture. How much of the 10% alcohol mixture and pure alcohol will you need to obtain the desired solution?

Answer 1

x + .1(630-x) = 630(.5) = 315

.9x = 315 -63 = 252

x = 252/.9 = 280 mL of pure alcohol mixed with 630-280 = 350 mL of 10% alcohol yields 630 mL of 50%

10 is within 40 of 50

100 is within 50 of 50

50/40 = 5/4

350/280 = 5/4