50 ounces of 15% saline solution contains 0.15*50 = 7.5 ounces of salt.
Let x be the amount of pure water you add to this solution. Then you end up with (x + 50) ounces of this new solution. The amount of salt stays the same.
You want the new solution to have a concentration of 10%. This means you need
7.5 / (x + 50) = 0.1
==> 7.5 = 0.1(x + 50)
==> 7.5 = 0.1x + 5
==> 2.5 = 0.1x
==> 2.5/0.1 = 0.1x/0.1
==> x = 25
Answer:
5.86666666667
Step-by-step explanation:
Answer:
92 attendees had activity cards
Step-by-step explanation:
Let x be the number of students with activity cards. Then 130-x is the number without, and the total revenue is ...
7x +10(130 -x) = 1024
7x +1300 -10x = 1024 . . . . eliminate parentheses
-3x = -276 . . . . . . . . . . . . . collect terms; subtract 1300
x = 92 . . . . . . divide by 3
92 students with activity cards attended the dance.
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<em>Comment on the solution</em>
Often, you will see such a problem solved using two equations. For example, they might be ...
Let 'a' represent the number with an activity card; 'w' the number without. Then ...
- a+w = 130 . . . . the total number of students
- 7a +10w = 1024 . . . . the revenue from ticket sales
The problem statement asks for the value of 'a', so you want to eliminate w from these equations. You can do that using substitution. Using the first equation to write an expression for w, you have ...
w = 130-a
and making the substitution into the second equation gives ...
7a +10(130 -a) = 1024
This should look a lot like the equation we used above. There, we skipped the extra variable and went straight to the single equation we needed to solve.
Answer:
D.f(x)=2x-9and g(x)=X+9/2
