Respuesta :
active + active = active
0.25x + 0.10*5 = 0.20(x+5)
25x + 10*5 = 20x + 20*5
5x = 10*5
x = 10 cups (amt. of 25% bleach used)
Answer:
10
Step-by-step explanation:
We will use a system of equations to solve this. We do not know how much of the 25% bleach solution is used; we will use x to represent this. We know that 5 cups of the 10% solution was used. We do not know how much of the resulting solution we have; we will use y to represent this. This gives us the equation
x+5 = y
Using the decimal forms of the percentages for each solution, we have 0.25x (25% solution for x cups), 0.1(5) (10% solution for 5 cups) and 0.2y (20% solution for y cups); this gives us the equation
0.25x+0.1(5) = 0.2y
This gives us the system
[tex]\left \{ {{x+5=y} \atop {0.25x+0.1(5)=0.2y}} \right.[/tex]
To use elimination, we will make the coefficients of x the same by multiplying the top equation by 0.25:
[tex]\left \{ {{0.25(x+5=y)} \atop {0.25x+0.5=0.2y}} \right. \\\\\left \{ {{0.25x+1.25=0.25y} \atop {0.25x+0.5=0.2y}} \right.[/tex]
We will now subtract the second equation from the first:
[tex]\left \{ {{0.25x+1.25=0.25y} \atop {-(0.25x+0.5=0.2y)}} \right. \\\\0.75 = 0.05y[/tex]
Divide both sides by 0.05:
0.75/0.05 = 0.05y/0.05
15 = y
There were 15 cups of the resulting 20% solution. Substituting this into the first equation, we have
x+5=15
Subtract 5 from each side:
x+5-5=15-5
x = 10
