00:01
So we're going to translate this situation into a system of equations and then solve it.
00:04
A scientist needs 120 milliliters of a 20 % acid solution for an experiment.
00:10
The lab has available a 25 % and a 10 % solution.
00:14
How many liters of the 25 %? how many liters of the 10 % should the scientists mix to make the 20 % solution? so because we're looking for the amount of 25 % and 10%, we'll call those x and y.
00:25
The goal is 120 milliliters.
00:28
So i'm going to model that with x plus y, equals 120.
00:32
Now i can model the concentration.
00:34
So i got 0 .25 times x plus 0 .10 times y.
00:39
And the goal is to get to 20%.
00:41
So that's 0 .20.
00:43
But that is multiplied by 120 for that's the amount that we're trying to get.
00:49
Okay.
00:49
So if i multiply that together and rewrite both of these, i got x plus y equals 120.
00:55
0 .25x plus 0 .20...