You need a 50% alcohol solution. On hand, you have a 195 mL of a 10% alcohol mixture. You also have 65% alcohol mixture.

Question

How much of the 65% mixture will you need to add to obtain the desired solution?

Answer 1

One way to solve this problem is by using the method of alligation, If you aren't familiar with this, you should look it up and read about it. It's quite simple.

Alligation:

Have .......... Want ........... Need

10%....................................15 parts

.......................50%..........................

65%.....................................40 parts

15 parts = 195 ml

40 parts therefore equals 2.666x that or 520 ml

So you should add 521 mls of 65% to the 195 mls of 10% to get a 50% solution.

Algebraic:

(x ml * 65%) + (195 ml *10%) = (195ml + x ml )(50%)

65x + 1950 = 9750 + 50x

15x = 7800

x = 520 mls

Add 520 mls of 65% to the 195 ml of 10% to get 50%