SOLUTION: how many quarts of pure antifreeze must be added to 8 quarts of a 50% antifreeze solution to obtain a 60% antifreeze ?''.

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Question 1091613: how many quarts of pure antifreeze must be added to 8 quarts of a 50% antifreeze solution to obtain a 60% antifreeze ?''.

Found 2 solutions by richwmiller, ikleyn:
Answer by richwmiller(17219)   (Show Source):
You can put this solution on YOUR website!
1.00*x+.5*8=.6(8.0+x)
x+4=4.8+.6x
.4x=.8
x=2
check
2+4=.6(10)
6=6
check

Answer by ikleyn(52781)   (Show Source):
You can put this solution on YOUR website!
.

Let x be the volume of the pure antifreeze under the question, in quarts. 8 quarts of the 50% antifreeze solution contain 0.5*8 quarts of the pure antifreeze. When we add x quarts of the pure antifreeze, the amount of pure antifreeze becomes x + 0.5*8 quarts. The total volume of liquid solution becomes (x+8) quarts. Therefore, the antifreeze concentration after adding becomes . According to the condition, it must be 60% = 0.6. It gives you an equation = 0.6. To solve it, first multiply both sides by (x+8). You will get x + 4 = 0.6*(x+8), or x + 4 = 0.6x + 4.8 ====> x - 0.6x = 4.8 - 4 ====> 0.4x = 0.8 ====> x = = 2. Answer. 2 quarts of the pure antifreeze must be added.

Solved.

There is entire bunch of introductory lessons covering various types of mixture problems
    - Mixture problems
    - More Mixture problems
    - Solving typical word problems on mixtures for solutions
    - Word problems on mixtures for antifreeze solutions (*)
    - Word problems on mixtures for alloys
    - Typical word problems on mixtures from the archive
in this site.

Among them, find the lesson on antifreeze marked by (*).
Read these lessons and become an expert in solving mixture word problems.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook in the section "Word problems" under the topic "Mixture problems".