Draining the Antifreeze

1
Draining the Antifreeze

• A Very Confusing
• Mixture Problem

2
The Problem
Your car can hold 12 liters of anti-freeze. It
currently has a 10 antifreeze solution. Winter
is on the way! How much antifreeze do you need
to drain and replace with pure antifreeze to make
it a 25 solution?
3
The Confusion

1. Drain? We have only done problems where we add
   things together. Drain? What am I supposed to do
   with drain?
2. Pure antifreeze? Why did they say pure antifreeze?

4
The Confusion

1. Drain?
2. We are mentally going to drain all the antifreeze
   and put it in a pail.
3. Then were going to add antifreeze from the pail
   and some pure antifreeze.
4. Voila! - a familiar mixture problem.
5. Pure anti-freeze? The percentage of antifreeze in
   pure anti-freeze is 100.

5
Lets make our boxes
liters Liters antifreeze
old mix x 10 10x
Pure 12 - x 100 100( 12 x)
New mix 12 25 300
6
Lets make our equation
Liters antifreeze
Antifreeze in old mix 10x
Antifreeze in pure 100( 12 x)
Antifreeze in new mix 300
10x 100( 12 x) 300
7
Now lets solve
10x 100( 12 x) 300 10x 1200 - 100x
300 - 90x 300 1200
- 90x - 900
x 10
8
Now lets check
Weve kept 10 liters of our old 10 solution.
Thats 1 liter of antifreeze. We have 2 liters of
the pure stuff. Thats 2 liters of antifreeze. 1
2 3 liters of antifreeze. We wanted 25 of
the 12 liters to be antifreeze. 25 of 12 .25 (
12 ) 3 Hooray!
9
Dont Allow Brain Drain!

• Drain?
• Drain it all into a pail and mix it back in like
  a regular problem.
• Pure Antifreeze?
• 100 antifreeze