SOLUTION: 1. in order to increase the concentration of 25g of 5% salt solution in water to 15% salt, how much salt will be added? 2. an auto mechanic added 25ml of water to 125ml of a 2

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Question 155642This question is from textbook prentice hall algebra 1
: 1. in order to increase the concentration of 25g of 5% salt solution in water to 15% salt, how much salt will be added?
2. an auto mechanic added 25ml of water to 125ml of a 20% solution of antifreeze in water. what is the concentration of antifreeze in the new solution?
3. jorge added 15g of ground costa rican coffee to 210g of a ground mixture that contains 5% costa rican coffee. what is the percent of costa rican coffee in his new solution?
thanks for helping.. God bless..
This question is from textbook prentice hall algebra 1

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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1. in order to increase the concentration of 25g of 5% salt solution in water to 15% salt, how much salt will be added?
;
Let x = amt (in grams) of salt required:
:
Write an equation representing the amt of salt:
:
.05(25) + x = .15(x+25)
;
1.25 + x = .15x + 3.75
:
x = .15x = 3.75 - 1.25
:
.85x = 2.5
x = 2.5%2F.85
x = 2.94 gr of salt
;
Check solution:
.05(25) + 2.94 = .15(2.94+25)
4.19 = 4.19
:
;
2. an auto mechanic added 25ml of water to 125ml of a 20% solution of antifreeze in water. what is the concentration of antifreeze in the new solution?
:
Let x = decimal equiv of % of the new solution
:
.20(125) = x(125 + 25)
:
25 = 150x
x = 25%2F125
x = .1665 which 16.67%
;
Check:
25 = .1667(150)
25 = 25.0
:
:
3. jorge added 15g of ground costa rican coffee to 210g of a ground mixture that contains 5% costa rican coffee. what is the percent of costa rican coffee in his new solution?
;
Let x = decimal equiv of % result
.05(210) + 15 = x(210+15)
10.5 + 15 = 225x
x = 25.5%2F225
x = .1133 which is 11.33%
;
Check:
25.5 = .1133(225)
25.5 = 25.4925 ~ 25.5
;
:
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