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I will solve only one problem for you.
2. Mixture Problem
How much water must be evaporated from 80 pounds of a 12% solution of salt in order to obtain a 20% solution?
Let W be the MASS of water to evaporate, in pounds.
The amount of salt in the original 80 pounds of the 12% solution was 0.12*80 = 9.6 pounds.
When W pounds of water were evaporated, the remaining mass became 80 pounds - W pounds.
We want the new salt concentration be 20%. It means
= 0.2. (1)
(Notice that when the water evaporates, the mass of salt REMAINS the SAME (!) )
To solve equation (1), multiply both sides by (80-W). You will get
9.6 = 0.2*(80-W).
Simplify and find W.
9.6 = 0.2*80 - 0.2W
0.2W = 0.2*80 - 9.6 = 6.4,
W = = 32 pounds.
ANSWER. 32 pounds of water should be evaporated.
CHECK. I will check equation (1) for the concentration
= = 0.2, which is precisely correct (!)
Solved.
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It is a standard and typical mixture problem.
In this site, there is a bunch of lessons, covering various types of mixture problems. See introductory lessons
- 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
Read them and become an expert in solution the 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 online textbook under the topic "Mixture problems".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.